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feat: add solutions to lc/lcof2 problem: Combinations
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+449
-20
lines changed

15 files changed

+449
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‎lcof2/剑指 Offer II 080. 含有 k 个元素的组合/README.md

+88-2
Original file line numberDiff line numberDiff line change
@@ -41,27 +41,113 @@
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<p><meta charset="UTF-8" />注意：本题与主站 77&nbsp;题相同：&nbsp;<a href="https://leetcode-cn.com/problems/combinations/">https://leetcode-cn.com/problems/combinations/</a></p>
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## 解法
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<!-- 这里可写通用的实现逻辑 -->
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深度优先搜索 DFS。
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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 combine(self, n: int, k: int) -> List[List[int]]:
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res = []
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def dfs(i, n, k, t):
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if len(t) == k:
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res.append(t.copy())
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return
65+
for j in range(i, n + 1):
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t.append(j)
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dfs(j + 1, n, k, t)
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t.pop()
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dfs(1, n, k, [])
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return res
5772
```
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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 List<List<Integer>> combine(int n, int k) {
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List<List<Integer>> res = new ArrayList<>();
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dfs(1, n, k, new ArrayList<>(), res);
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return res;
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}
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private void dfs(int i, int n, int k, List<Integer> t, List<List<Integer>> res) {
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if (t.size() == k) {
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res.add(new ArrayList<>(t));
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return;
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}
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for (int j = i; j <= n; ++j) {
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t.add(j);
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dfs(j + 1, n, k, t, res);
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t.remove(t.size() - 1);
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}
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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<vector<int>> combine(int n, int k) {
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vector<vector<int>> res;
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vector<int> t;
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dfs(1, n, k, t, res);
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return res;
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}
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void dfs(int i, int n, int k, vector<int> t, vector<vector<int>>& res) {
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if (t.size() == k)
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{
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res.push_back(t);
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return;
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}
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for (int j = i; j <= n; ++j)
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{
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t.push_back(j);
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dfs(j + 1, n, k, t, res);
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t.pop_back();
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}
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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 combine(n int, k int) [][]int {
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var res [][]int
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var t []int
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dfs(1, n, k, t, &res)
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return res
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}
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func dfs(i, n, k int, t []int, res *[][]int) {
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if len(t) == k {
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cp := make([]int, k)
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copy(cp, t)
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*res = append(*res, cp)
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return
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}
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for j := i; j <= n; j++ {
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t = append(t, j)
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dfs(j+1, n, k, t, res)
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t = t[:len(t)-1]
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}
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}
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```
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### **...**

‎lcof2/剑指 Offer II 080. 含有 k 个元素的组合/Solution.cpp

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@@ -0,0 +1,23 @@
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class Solution {
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public:
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vector<vector<int>> combine(int n, int k) {
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vector<vector<int>> res;
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vector<int> t;
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dfs(1, n, k, t, res);
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return res;
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}
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void dfs(int i, int n, int k, vector<int> t, vector<vector<int>>& res) {
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if (t.size() == k)
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{
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res.push_back(t);
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return;
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}
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for (int j = i; j <= n; ++j)
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{
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t.push_back(j);
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dfs(j + 1, n, k, t, res);
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t.pop_back();
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}
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}
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};

‎lcof2/剑指 Offer II 080. 含有 k 个元素的组合/Solution.go

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
func combine(n int, k int) [][]int {
2+
var res [][]int
3+
var t []int
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dfs(1, n, k, t, &res)
5+
return res
6+
}
7+
8+
func dfs(i, n, k int, t []int, res *[][]int) {
9+
if len(t) == k {
10+
cp := make([]int, k)
11+
copy(cp, t)
12+
*res = append(*res, cp)
13+
return
14+
}
15+
for j := i; j <= n; j++ {
16+
t = append(t, j)
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dfs(j+1, n, k, t, res)
18+
t = t[:len(t)-1]
19+
}
20+
}

‎lcof2/剑指 Offer II 080. 含有 k 个元素的组合/Solution.java

+19
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
class Solution {
2+
public List<List<Integer>> combine(int n, int k) {
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List<List<Integer>> res = new ArrayList<>();
4+
dfs(1, n, k, new ArrayList<>(), res);
5+
return res;
6+
}
7+
8+
private void dfs(int i, int n, int k, List<Integer> t, List<List<Integer>> res) {
9+
if (t.size() == k) {
10+
res.add(new ArrayList<>(t));
11+
return;
12+
}
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for (int j = i; j <= n; ++j) {
14+
t.add(j);
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dfs(j + 1, n, k, t, res);
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t.remove(t.size() - 1);
17+
}
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}
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}

‎lcof2/剑指 Offer II 080. 含有 k 个元素的组合/Solution.py

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
1+
class Solution:
2+
def combine(self, n: int, k: int) -> List[List[int]]:
3+
res = []
4+
5+
def dfs(i, n, k, t):
6+
if len(t) == k:
7+
res.append(t.copy())
8+
return
9+
for j in range(i, n + 1):
10+
t.append(j)
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dfs(j + 1, n, k, t)
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t.pop()
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dfs(1, n, k, [])
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return res

‎solution/0000-0099/0077.Combinations/README.md

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Original file line numberDiff line numberDiff line change
@@ -21,27 +21,113 @@
2121
[1,4],
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]</pre>
2323

24-
2524
## 解法
2625

2726
<!-- 这里可写通用的实现逻辑 -->
2827

28+
深度优先搜索 DFS。
29+
2930
<!-- tabs:start -->
3031

3132
### **Python3**
3233

3334
<!-- 这里可写当前语言的特殊实现逻辑 -->
3435

3536
```python
36-
37+
class Solution:
38+
def combine(self, n: int, k: int) -> List[List[int]]:
39+
res = []
40+
41+
def dfs(i, n, k, t):
42+
if len(t) == k:
43+
res.append(t.copy())
44+
return
45+
for j in range(i, n + 1):
46+
t.append(j)
47+
dfs(j + 1, n, k, t)
48+
t.pop()
49+
50+
dfs(1, n, k, [])
51+
return res
3752
```
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3954
### **Java**
4055

4156
<!-- 这里可写当前语言的特殊实现逻辑 -->
4257

4358
```java
59+
class Solution {
60+
public List<List<Integer>> combine(int n, int k) {
61+
List<List<Integer>> res = new ArrayList<>();
62+
dfs(1, n, k, new ArrayList<>(), res);
63+
return res;
64+
}
65+
66+
private void dfs(int i, int n, int k, List<Integer> t, List<List<Integer>> res) {
67+
if (t.size() == k) {
68+
res.add(new ArrayList<>(t));
69+
return;
70+
}
71+
for (int j = i; j <= n; ++j) {
72+
t.add(j);
73+
dfs(j + 1, n, k, t, res);
74+
t.remove(t.size() - 1);
75+
}
76+
}
77+
}
78+
```
79+
80+
### **C++**
81+
82+
```cpp
83+
class Solution {
84+
public:
85+
vector<vector<int>> combine(int n, int k) {
86+
vector<vector<int>> res;
87+
vector<int> t;
88+
dfs(1, n, k, t, res);
89+
return res;
90+
}
91+
92+
void dfs(int i, int n, int k, vector<int> t, vector<vector<int>>& res) {
93+
if (t.size() == k)
94+
{
95+
res.push_back(t);
96+
return;
97+
}
98+
for (int j = i; j <= n; ++j)
99+
{
100+
t.push_back(j);
101+
dfs(j + 1, n, k, t, res);
102+
t.pop_back();
103+
}
104+
}
105+
};
106+
```
44107

108+
### **Go**
109+
110+
```go
111+
func combine(n int, k int) [][]int {
112+
var res [][]int
113+
var t []int
114+
dfs(1, n, k, t, &res)
115+
return res
116+
}
117+
118+
func dfs(i, n, k int, t []int, res *[][]int) {
119+
if len(t) == k {
120+
cp := make([]int, k)
121+
copy(cp, t)
122+
*res = append(*res, cp)
123+
return
124+
}
125+
for j := i; j <= n; j++ {
126+
t = append(t, j)
127+
dfs(j+1, n, k, t, res)
128+
t = t[:len(t)-1]
129+
}
130+
}
45131
```
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47133
### **...**

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