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feat: add solutions to lc problem: No.0750 (#1362)
No.0750.Number Of Corner Rectangles
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‎solution/0700-0799/0750.Number Of Corner Rectangles/README.md

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<!-- 这里可写通用的实现逻辑 -->
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**方法一：哈希表 + 枚举**
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我们枚举每一行作为矩形的下边，对于当前行，如果列 $i$ 和列 $j$ 都是 $1$，那么我们用哈希表找出此前的所有行中，有多少行的 $i$ 和 $j$ 列都是 $1$，那么就有多少个以 $(i, j)$ 为右下角的矩形，我们将其数量加入答案。然后将 $(i, j)$ 加入哈希表，继续枚举下一对 $(i, j)$。
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时间复杂度 $O(m \times n^2)$，空间复杂度 $O(n^2)$。其中 $m$ 和 $n$ 分别是矩阵的行数和列数。
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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 countCornerRectangles(self, grid: List[List[int]]) -> int:
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ans = 0
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cnt = Counter()
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n = len(grid[0])
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for row in grid:
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for i, c1 in enumerate(row):
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if c1:
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for j in range(i + 1, n):
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if row[j]:
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ans += cnt[(i, j)]
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cnt[(i, j)] += 1
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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 countCornerRectangles(int[][] grid) {
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int n = grid[0].length;
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int ans = 0;
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Map<List<Integer>, Integer> cnt = new HashMap<>();
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for (var row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i] == 1) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j] == 1) {
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List<Integer> t = List.of(i, j);
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ans += cnt.getOrDefault(t, 0);
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cnt.merge(t, 1, Integer::sum);
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}
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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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int countCornerRectangles(vector<vector<int>>& grid) {
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int n = grid[0].size();
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int ans = 0;
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map<pair<int, int>, int> cnt;
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for (auto& row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i]) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j]) {
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ans += cnt[{i, j}];
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++cnt[{i, j}];
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}
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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 countCornerRectangles(grid [][]int) (ans int) {
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n := len(grid[0])
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type pair struct{ x, y int }
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cnt := map[pair]int{}
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for _, row := range grid {
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for i, x := range row {
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if x == 1 {
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for j := i + 1; j < n; j++ {
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if row[j] == 1 {
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t := pair{i, j}
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ans += cnt[t]
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cnt[t]++
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}
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}
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}
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}
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}
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return
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}
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```
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### **TypeScript**
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```ts
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function countCornerRectangles(grid: number[][]): number {
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const n = grid[0].length;
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let ans = 0;
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const cnt: Map<number, number> = new Map();
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for (const row of grid) {
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for (let i = 0; i < n; ++i) {
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if (row[i] === 1) {
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for (let j = i + 1; j < n; ++j) {
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if (row[j] === 1) {
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const t = i * 200 + j;
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ans += cnt.get(t) ?? 0;
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cnt.set(t, (cnt.get(t) ?? 0) + 1);
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}
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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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### **...**

‎solution/0700-0799/0750.Number Of Corner Rectangles/README_EN.md

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### **Python3**
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```python
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class Solution:
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def countCornerRectangles(self, grid: List[List[int]]) -> int:
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ans = 0
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cnt = Counter()
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n = len(grid[0])
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for row in grid:
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for i, c1 in enumerate(row):
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if c1:
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for j in range(i + 1, n):
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if row[j]:
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ans += cnt[(i, j)]
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cnt[(i, j)] += 1
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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 countCornerRectangles(int[][] grid) {
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int n = grid[0].length;
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int ans = 0;
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Map<List<Integer>, Integer> cnt = new HashMap<>();
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for (var row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i] == 1) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j] == 1) {
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List<Integer> t = List.of(i, j);
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ans += cnt.getOrDefault(t, 0);
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cnt.merge(t, 1, Integer::sum);
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}
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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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int countCornerRectangles(vector<vector<int>>& grid) {
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int n = grid[0].size();
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int ans = 0;
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map<pair<int, int>, int> cnt;
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for (auto& row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i]) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j]) {
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ans += cnt[{i, j}];
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++cnt[{i, j}];
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}
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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 countCornerRectangles(grid [][]int) (ans int) {
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n := len(grid[0])
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type pair struct{ x, y int }
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cnt := map[pair]int{}
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for _, row := range grid {
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for i, x := range row {
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if x == 1 {
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for j := i + 1; j < n; j++ {
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if row[j] == 1 {
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t := pair{i, j}
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ans += cnt[t]
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cnt[t]++
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}
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}
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}
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}
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}
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return
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}
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```
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### **TypeScript**
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```ts
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function countCornerRectangles(grid: number[][]): number {
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const n = grid[0].length;
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let ans = 0;
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const cnt: Map<number, number> = new Map();
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for (const row of grid) {
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for (let i = 0; i < n; ++i) {
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if (row[i] === 1) {
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for (let j = i + 1; j < n; ++j) {
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if (row[j] === 1) {
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const t = i * 200 + j;
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ans += cnt.get(t) ?? 0;
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cnt.set(t, (cnt.get(t) ?? 0) + 1);
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}
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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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### **...**

‎solution/0700-0799/0750.Number Of Corner Rectangles/Solution.cpp

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class Solution {
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public:
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int countCornerRectangles(vector<vector<int>>& grid) {
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int n = grid[0].size();
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int ans = 0;
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map<pair<int, int>, int> cnt;
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for (auto& row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i]) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j]) {
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ans += cnt[{i, j}];
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++cnt[{i, j}];
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}
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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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};

‎solution/0700-0799/0750.Number Of Corner Rectangles/Solution.go

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func countCornerRectangles(grid [][]int) (ans int) {
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n := len(grid[0])
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type pair struct{ x, y int }
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cnt := map[pair]int{}
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for _, row := range grid {
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for i, x := range row {
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if x == 1 {
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for j := i + 1; j < n; j++ {
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if row[j] == 1 {
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t := pair{i, j}
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ans += cnt[t]
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cnt[t]++
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}
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}
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}
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}
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}
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return
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}

‎solution/0700-0799/0750.Number Of Corner Rectangles/Solution.java

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class Solution {
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public int countCornerRectangles(int[][] grid) {
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int n = grid[0].length;
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int ans = 0;
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Map<List<Integer>, Integer> cnt = new HashMap<>();
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for (var row : grid) {
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for (int i = 0; i < n; ++i) {
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if (row[i] == 1) {
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for (int j = i + 1; j < n; ++j) {
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if (row[j] == 1) {
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List<Integer> t = List.of(i, j);
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ans += cnt.getOrDefault(t, 0);
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cnt.merge(t, 1, Integer::sum);
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}
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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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}

‎solution/0700-0799/0750.Number Of Corner Rectangles/Solution.py

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class Solution:
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def countCornerRectangles(self, grid: List[List[int]]) -> int:
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ans = 0
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cnt = Counter()
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n = len(grid[0])
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for row in grid:
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for i, c1 in enumerate(row):
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if c1:
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for j in range(i + 1, n):
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if row[j]:
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ans += cnt[(i, j)]
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cnt[(i, j)] += 1
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return ans

‎solution/0700-0799/0750.Number Of Corner Rectangles/Solution.ts

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function countCornerRectangles(grid: number[][]): number {
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const n = grid[0].length;
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let ans = 0;
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const cnt: Map<number, number> = new Map();
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for (const row of grid) {
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for (let i = 0; i < n; ++i) {
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if (row[i] === 1) {
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for (let j = i + 1; j < n; ++j) {
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if (row[j] === 1) {
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const t = i * 200 + j;
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ans += cnt.get(t) ?? 0;
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cnt.set(t, (cnt.get(t) ?? 0) + 1);
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}
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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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