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feat: add solutions to lcci problem: No.17.24
No.17.24.Max Submatrix
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‎lcci/17.24.Max Submatrix/README.md

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@@ -31,22 +31,175 @@
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<!-- 这里可写通用的实现逻辑 -->
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双指针 i1, i2 遍历所有可能的“行对”，即子矩阵的上下两条边，这决定了矩阵的高，然后枚举 i1~i2 高度的每一列，看成一维数组的一项，求和最大的子数组即可。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def getMaxMatrix(self, matrix: List[List[int]]) -> List[int]:
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m, n = len(matrix), len(matrix[0])
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s = [[0] * n for _ in range(m + 1)]
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for i in range(m):
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for j in range(n):
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# 构造列前缀和
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s[i + 1][j] = s[i][j] + matrix[i][j]
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mx = matrix[0][0]
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ans = [0, 0, 0, 0]
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for i1 in range(m):
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for i2 in range(i1, m):
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nums = [0] * n
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for j in range(n):
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nums[j] = s[i2 + 1][j] - s[i1][j]
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start = 0
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f = nums[0]
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for j in range(1, n):
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if f > 0:
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f += nums[j]
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else:
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f = nums[j]
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start = j
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if f > mx:
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mx = f
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ans = [i1, start, i2, j]
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return ans
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int[] getMaxMatrix(int[][] matrix) {
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int m = matrix.length, n = matrix[0].length;
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int[][] s = new int[m + 1][n];
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for (int i = 0; i < m; ++i) {
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for (int j = 0; j < n; ++j) {
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s[i + 1][j] = s[i][j] + matrix[i][j];
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}
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}
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int mx = matrix[0][0];
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int[] ans = new int[]{0, 0, 0, 0};
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for (int i1 = 0; i1 < m; ++i1) {
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for (int i2 = i1; i2 < m; ++i2) {
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int[] nums = new int[n];
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for (int j = 0; j < n; ++j) {
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nums[j] = s[i2 + 1][j] - s[i1][j];
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}
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int start = 0;
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int f = nums[0];
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for (int j = 1; j < n; ++j) {
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if (f > 0) {
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f += nums[j];
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} else {
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f = nums[j];
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start = j;
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}
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if (f > mx) {
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mx = f;
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ans = new int[]{i1, start, i2, j};
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}
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}
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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vector<int> getMaxMatrix(vector<vector<int>>& matrix) {
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int m = matrix.size(), n = matrix[0].size();
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vector<vector<int>> s(m + 1, vector<int>(n));
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for (int i = 0; i < m; ++i)
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for (int j = 0; j < n; ++j)
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s[i + 1][j] = s[i][j] + matrix[i][j];
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int mx = matrix[0][0];
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vector<int> ans(4);
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for (int i1 = 0; i1 < m; ++i1)
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{
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for (int i2 = i1; i2 < m; ++i2)
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{
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vector<int> nums;
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for (int j = 0; j < n; ++j)
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nums.push_back(s[i2 + 1][j] - s[i1][j]);
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int start = 0;
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int f = nums[0];
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for (int j = 1; j < n; ++j)
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{
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if (f > 0) f += nums[j];
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else
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{
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f = nums[j];
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start = j;
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}
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if (f > mx)
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{
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mx = f;
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ans[0] = i1;
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ans[1] = start;
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ans[2] = i2;
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ans[3] = j;
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}
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}
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}
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func getMaxMatrix(matrix [][]int) []int {
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m, n := len(matrix), len(matrix[0])
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s := make([][]int, m+1)
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for i := range s {
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s[i] = make([]int, n)
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}
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for i := 0; i < m; i++ {
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for j := 0; j < n; j++ {
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s[i+1][j] = s[i][j] + matrix[i][j]
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}
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}
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mx := matrix[0][0]
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ans := make([]int, 4)
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for i1 := 0; i1 < m; i1++ {
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for i2 := i1; i2 < m; i2++ {
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var nums []int
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for j := 0; j < n; j++ {
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nums = append(nums, s[i2+1][j]-s[i1][j])
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}
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start := 0
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f := nums[0]
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for j := 1; j < n; j++ {
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if f > 0 {
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f += nums[j]
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} else {
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f = nums[j]
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start = j
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}
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if f > mx {
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mx = f
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ans = []int{i1, start, i2, j}
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}
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}
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}
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}
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return ans
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}
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```
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### **...**

‎lcci/17.24.Max Submatrix/README_EN.md

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@@ -39,13 +39,163 @@
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### **Python3**
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```python
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class Solution:
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def getMaxMatrix(self, matrix: List[List[int]]) -> List[int]:
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m, n = len(matrix), len(matrix[0])
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s = [[0] * n for _ in range(m + 1)]
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for i in range(m):
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for j in range(n):
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s[i + 1][j] = s[i][j] + matrix[i][j]
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mx = matrix[0][0]
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ans = [0, 0, 0, 0]
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for i1 in range(m):
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for i2 in range(i1, m):
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nums = [0] * n
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for j in range(n):
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nums[j] = s[i2 + 1][j] - s[i1][j]
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start = 0
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f = nums[0]
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for j in range(1, n):
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if f > 0:
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f += nums[j]
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else:
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f = nums[j]
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start = j
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if f > mx:
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mx = f
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ans = [i1, start, i2, j]
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return ans
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```
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### **Java**
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```java
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class Solution {
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public int[] getMaxMatrix(int[][] matrix) {
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int m = matrix.length, n = matrix[0].length;
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int[][] s = new int[m + 1][n];
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for (int i = 0; i < m; ++i) {
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for (int j = 0; j < n; ++j) {
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s[i + 1][j] = s[i][j] + matrix[i][j];
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}
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}
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int mx = matrix[0][0];
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int[] ans = new int[]{0, 0, 0, 0};
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for (int i1 = 0; i1 < m; ++i1) {
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for (int i2 = i1; i2 < m; ++i2) {
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int[] nums = new int[n];
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for (int j = 0; j < n; ++j) {
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nums[j] = s[i2 + 1][j] - s[i1][j];
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}
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int start = 0;
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int f = nums[0];
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for (int j = 1; j < n; ++j) {
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if (f > 0) {
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f += nums[j];
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} else {
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f = nums[j];
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start = j;
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}
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if (f > mx) {
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mx = f;
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ans = new int[]{i1, start, i2, j};
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}
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}
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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vector<int> getMaxMatrix(vector<vector<int>>& matrix) {
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int m = matrix.size(), n = matrix[0].size();
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vector<vector<int>> s(m + 1, vector<int>(n));
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for (int i = 0; i < m; ++i)
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for (int j = 0; j < n; ++j)
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s[i + 1][j] = s[i][j] + matrix[i][j];
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int mx = matrix[0][0];
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vector<int> ans(4);
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for (int i1 = 0; i1 < m; ++i1)
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{
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for (int i2 = i1; i2 < m; ++i2)
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{
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vector<int> nums;
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for (int j = 0; j < n; ++j)
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nums.push_back(s[i2 + 1][j] - s[i1][j]);
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int start = 0;
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int f = nums[0];
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for (int j = 1; j < n; ++j)
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{
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if (f > 0) f += nums[j];
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else
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{
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f = nums[j];
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start = j;
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}
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if (f > mx)
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{
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mx = f;
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ans[0] = i1;
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ans[1] = start;
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ans[2] = i2;
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ans[3] = j;
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}
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}
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}
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func getMaxMatrix(matrix [][]int) []int {
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m, n := len(matrix), len(matrix[0])
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s := make([][]int, m+1)
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for i := range s {
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s[i] = make([]int, n)
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}
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for i := 0; i < m; i++ {
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for j := 0; j < n; j++ {
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s[i+1][j] = s[i][j] + matrix[i][j]
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}
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}
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mx := matrix[0][0]
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ans := make([]int, 4)
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for i1 := 0; i1 < m; i1++ {
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for i2 := i1; i2 < m; i2++ {
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var nums []int
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for j := 0; j < n; j++ {
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nums = append(nums, s[i2+1][j]-s[i1][j])
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}
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start := 0
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f := nums[0]
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for j := 1; j < n; j++ {
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if f > 0 {
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f += nums[j]
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} else {
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f = nums[j]
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start = j
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}
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if f > mx {
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mx = f
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ans = []int{i1, start, i2, j}
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}
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}
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}
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}
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return ans
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}
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```
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### **...**

‎lcci/17.24.Max Submatrix/Solution.cpp

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class Solution {
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public:
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vector<int> getMaxMatrix(vector<vector<int>>& matrix) {
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int m = matrix.size(), n = matrix[0].size();
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vector<vector<int>> s(m + 1, vector<int>(n));
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for (int i = 0; i < m; ++i)
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for (int j = 0; j < n; ++j)
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s[i + 1][j] = s[i][j] + matrix[i][j];
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int mx = matrix[0][0];
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vector<int> ans(4);
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for (int i1 = 0; i1 < m; ++i1)
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{
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for (int i2 = i1; i2 < m; ++i2)
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{
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vector<int> nums;
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for (int j = 0; j < n; ++j)
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nums.push_back(s[i2 + 1][j] - s[i1][j]);
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int start = 0;
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int f = nums[0];
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for (int j = 1; j < n; ++j)
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{
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if (f > 0) f += nums[j];
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else
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{
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f = nums[j];
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start = j;
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}
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if (f > mx)
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{
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mx = f;
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ans[0] = i1;
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ans[1] = start;
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ans[2] = i2;
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ans[3] = j;
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}
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}
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}
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}
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return ans;
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}
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};

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