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feat: update leetcode solutions: No.0046. Permutations
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‎solution/0000-0099/0046.Permutations/README.md

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Original file line numberDiff line numberDiff line change
@@ -30,16 +30,110 @@
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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回溯法：
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```python
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class Solution:
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def permute(self, nums: List[int]) -> List[List[int]]:
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def dfs(nums, i, res, path, used):
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if i == len(nums):
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res.append(copy.deepcopy(path))
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return
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for j in range(len(nums)):
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if not used[j]:
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path.append(nums[j])
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used[j] = True
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dfs(nums, i + 1, res, path, used)
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used[j] = False
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path.pop()
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res, path = [], []
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used = [False] * len(nums)
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dfs(nums, 0, res, path, used)
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return res
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```
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切分数组：
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```python
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class Solution:
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def permute(self, nums: List[int]) -> List[List[int]]:
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if len(nums) <= 1:
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return [nums]
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res = []
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for i, num in enumerate(nums):
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n = nums[:i] + nums[i + 1:]
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for item in self.permute(n):
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res.append([num] + item)
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return res
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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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回溯法：
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4177
```java
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class Solution {
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public List<List<Integer>> permute(int[] nums) {
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List<List<Integer>> res = new ArrayList<>();
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List<Integer> path = new ArrayList<>();
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boolean[] used = new boolean[nums.length];
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dfs(nums, 0, res, path, used);
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return res;
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}
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private void dfs(int[] nums, int i, List<List<Integer>> res, List<Integer> path, boolean[] used) {
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if (i == nums.length) {
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res.add(new ArrayList<>(path));
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return;
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}
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for (int j = 0; j < nums.length; ++j) {
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if (!used[j]) {
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path.add(nums[j]);
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used[j] = true;
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dfs(nums, i + 1, res, path, used);
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used[j] = false;
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path.remove(path.size() - 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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- 递归：
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```java
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class Solution {
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public List<List<Integer>> permute(int[] nums) {
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List<List<Integer>> res = new ArrayList<>();
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permute(res, nums, 0);
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return res;
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}
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private void permute(List<List<Integer>> res, int[] nums, int start) {
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if (start == nums.length) {
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List<Integer> t = new ArrayList<>();
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for (int e : nums) {
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t.add(e);
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}
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res.add(t);
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return;
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}
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for (int i = start; i < nums.length; ++i) {
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swap(nums, i, start);
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permute(res, nums, start + 1);
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swap(nums, i, start);
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}
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}
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private void swap(int[] nums, int i, int j) {
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int t = nums[i];
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nums[i] = nums[j];
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nums[j] = t;
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}
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}
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```
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### **...**

‎solution/0000-0099/0046.Permutations/README_EN.md

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@@ -39,13 +39,82 @@
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### **Python3**
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```python
42-
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class Solution:
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def permute(self, nums: List[int]) -> List[List[int]]:
44+
if len(nums) <= 1:
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return [nums]
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res = []
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for i, num in enumerate(nums):
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n = nums[:i] + nums[i + 1:]
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for item in self.permute(n):
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res.append([num] + item)
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return res
4352
```
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4554
### **Java**
4655

56+
Backtracking:
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4758
```java
59+
class Solution {
60+
public List<List<Integer>> permute(int[] nums) {
61+
List<List<Integer>> res = new ArrayList<>();
62+
List<Integer> path = new ArrayList<>();
63+
boolean[] used = new boolean[nums.length];
64+
dfs(nums, 0, res, path, used);
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return res;
66+
}
67+
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private void dfs(int[] nums, int i, List<List<Integer>> res, List<Integer> path, boolean[] used) {
69+
if (i == nums.length) {
70+
res.add(new ArrayList<>(path));
71+
return;
72+
}
73+
for (int j = 0; j < nums.length; ++j) {
74+
if (!used[j]) {
75+
path.add(nums[j]);
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used[j] = true;
77+
dfs(nums, i + 1, res, path, used);
78+
used[j] = false;
79+
path.remove(path.size() - 1);
80+
}
81+
}
82+
}
83+
}
84+
```
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86+
- Recursion:
87+
88+
```java
89+
class Solution {
90+
public List<List<Integer>> permute(int[] nums) {
91+
List<List<Integer>> res = new ArrayList<>();
92+
permute(res, nums, 0);
93+
return res;
94+
}
95+
96+
private void permute(List<List<Integer>> res, int[] nums, int start) {
97+
if (start == nums.length) {
98+
List<Integer> t = new ArrayList<>();
99+
for (int e : nums) {
100+
t.add(e);
101+
}
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res.add(t);
103+
return;
104+
}
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for (int i = start; i < nums.length; ++i) {
106+
swap(nums, i, start);
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permute(res, nums, start + 1);
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swap(nums, i, start);
109+
}
110+
}
111+
112+
private void swap(int[] nums, int i, int j) {
113+
int t = nums[i];
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nums[i] = nums[j];
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nums[j] = t;
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}
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}
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```
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### **...**

‎solution/0000-0099/0046.Permutations/Solution.java

+15-15
Original file line numberDiff line numberDiff line change
@@ -1,27 +1,27 @@
11
class Solution {
22
public List<List<Integer>> permute(int[] nums) {
3-
List<List<Integer>> list = new ArrayList<>();
4-
permute(list, nums, 0);
5-
return list;
3+
List<List<Integer>> res = new ArrayList<>();
4+
permute(res, nums, 0);
5+
return res;
66
}
7-
8-
private void permute(List<List<Integer>> list, int[] nums, int start) {
9-
int end = nums.length - 1;
10-
if (start == end) {
11-
list.add(Arrays.stream(nums).boxed().collect(Collectors.toList()));
7+
8+
private void permute(List<List<Integer>> res, int[] nums, int start) {
9+
if (start == nums.length) {
10+
List<Integer> t = new ArrayList<>();
11+
for (int e : nums) {
12+
t.add(e);
13+
}
14+
res.add(t);
1215
return;
1316
}
14-
15-
for (int i = start; i <= end; ++i) {
17+
for (int i = start; i < nums.length; ++i) {
1618
swap(nums, i, start);
17-
permute(list, nums, start + 1);
19+
permute(res, nums, start + 1);
1820
swap(nums, i, start);
1921
}
20-
21-
2222
}
23-
24-
private static void swap(int[] nums, int i, int j) {
23+
24+
private void swap(int[] nums, int i, int j) {
2525
int t = nums[i];
2626
nums[i] = nums[j];
2727
nums[j] = t;

‎solution/0000-0099/0046.Permutations/Solution.py

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Original file line numberDiff line numberDiff line change
@@ -1,15 +1,10 @@
11
class Solution:
2-
def permute(self, nums):
3-
"""
4-
:type nums: List[int]
5-
:rtype: List[List[int]]
6-
"""
7-
if len(nums) <= 1:
2+
def permute(self, nums: List[int]) -> List[List[int]]:
3+
if len(nums) <= 1:
84
return [nums]
9-
ans = []
5+
res = []
106
for i, num in enumerate(nums):
11-
n = nums[:i] + nums[i+1:]
12-
for y in self.permute(n):
13-
ans.append([num] + y)
14-
return ans
15-
7+
n = nums[:i] + nums[i + 1:]
8+
for item in self.permute(n):
9+
res.append([num] + item)
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return res

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