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Commit 6f46b26

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Merge branch 'master' of github.com:youngyangyang04/leetcode-master
2 parents e5c4e9e + 1fcebdf commit 6f46b26

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50 files changed

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‎problems/0017.电话号码的字母组合.md‎

Lines changed: 33 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -260,7 +260,7 @@ class Solution {
260260

261261
}
262262

263-
//每次迭代获取一个字符串,所以会设计大量的字符串拼接,所以这里选择更为高效的 StringBuild
263+
//每次迭代获取一个字符串,所以会设计大量的字符串拼接,所以这里选择更为高效的 StringBuilder
264264
StringBuilder temp = new StringBuilder();
265265

266266
//比如digits如果为"23",num 为0,则str表示2对应的 abc
@@ -732,6 +732,38 @@ def backtracking(result, letter_map, digits, path, index)
732732
end
733733
end
734734
```
735+
### C#
736+
```C#
737+
public class Solution
738+
{
739+
public IList<string> res = new List<string>();
740+
public string s;
741+
public string[] letterMap = new string[10] { "", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" };
742+
public IList<string> LetterCombinations(string digits)
743+
{
744+
if (digits.Length == 0)
745+
return res;
746+
BackTracking(digits, 0);
747+
return res;
748+
}
749+
public void BackTracking(string digits, int index)
750+
{
751+
if (index == digits.Length)
752+
{
753+
res.Add(s);
754+
return;
755+
}
756+
int digit = digits[index] - '0';
757+
string letters = letterMap[digit];
758+
for (int i = 0; i < letters.Length; i++)
759+
{
760+
s += letters[i];
761+
BackTracking(digits, index + 1);
762+
s = s.Substring(0, s.Length - 1);
763+
}
764+
}
765+
}
766+
```
735767

736768
<p align="center">
737769
<a href="https://programmercarl.com/other/kstar.html" target="_blank">

‎problems/0019.删除链表的倒数第N个节点.md‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -106,7 +106,7 @@ public ListNode removeNthFromEnd(ListNode head, int n){
106106
ListNode slowIndex = dummyNode;
107107
108108
// 只要快慢指针相差 n 个结点即可
109-
for (int i = 0; i <= n ; i++){
109+
for (int i = 0; i < n ; i++){
110110
fastIndex = fastIndex.next;
111111
}
112112

‎problems/0020.有效的括号.md‎

Lines changed: 34 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -218,23 +218,41 @@ class Solution:
218218
### Go:
219219

220220
```Go
221+
// 思路: 使用栈来进行括号的匹配
222+
// 时间复杂度 O(n)
223+
// 空间复杂度 O(n)
221224
func isValid(s string) bool {
222-
hash := map[byte]byte{')':'(', ']':'[', '}':'{'}
223-
stack := make([]byte, 0)
224-
if s == "" {
225-
return true
226-
}
227-
228-
for i := 0; i < len(s); i++ {
229-
if s[i] == '(' || s[i] == '[' || s[i] == '{' {
230-
stack = append(stack, s[i])
231-
} else if len(stack) > 0 && stack[len(stack)-1] == hash[s[i]] {
232-
stack = stack[:len(stack)-1]
233-
} else {
234-
return false
235-
}
236-
}
237-
return len(stack) == 0
225+
// 使用切片模拟栈的行为
226+
stack := make([]rune, 0)
227+
228+
// m 用于记录某个右括号对应的左括号
229+
m := make(map[rune]rune)
230+
m[')'] = '('
231+
m[']'] = '['
232+
m['}'] = '{'
233+
234+
// 遍历字符串中的 rune
235+
for _, c := range s {
236+
// 左括号直接入栈
237+
if c == '(' || c == '[' || c == '{' {
238+
stack = append(stack, c)
239+
} else {
240+
// 如果是右括号,先判断栈内是否还有元素
241+
if len(stack) == 0 {
242+
return false
243+
}
244+
// 再判断栈顶元素是否能够匹配
245+
peek := stack[len(stack)-1]
246+
if peek != m[c] {
247+
return false
248+
}
249+
// 模拟栈顶弹出
250+
stack = stack[:len(stack)-1]
251+
}
252+
}
253+
254+
// 若栈中不再包含元素,则能完全匹配
255+
return len(stack) == 0
238256
}
239257
```
240258

‎problems/0024.两两交换链表中的节点.md‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -63,7 +63,9 @@ public:
6363

6464
cur = cur->next->next; // cur移动两位,准备下一轮交换
6565
}
66-
return dummyHead->next;
66+
ListNode* result = dummyHead->next;
67+
delete dummyHead;
68+
return result;
6769
}
6870
};
6971
```

‎problems/0027.移除元素.md‎

Lines changed: 17 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -256,17 +256,24 @@ class Solution:
256256
### Go:
257257

258258
```go
259+
// 快慢指针法
260+
// 时间复杂度 O(n)
261+
// 空间复杂度 O(1)
259262
func removeElement(nums []int, val int) int {
260-
length:=len(nums)
261-
res:=0
262-
for i:=0;i<length;i++{
263-
if nums[i]!=val {
264-
nums[res]=nums[i]
265-
res++
266-
}
267-
}
268-
nums=nums[:res]
269-
return res
263+
// 初始化慢指针 slow
264+
slow := 0
265+
// 通过 for 循环移动快指针 fast
266+
// 当 fast 指向的元素等于 val 时,跳过
267+
// 否则,将该元素写入 slow 指向的位置,并将 slow 后移一位
268+
for fast := 0; fast < len(nums); fast++ {
269+
if nums[fast] == val {
270+
continue
271+
}
272+
nums[slow] = nums[fast]
273+
slow++
274+
}
275+
276+
return slow
270277
}
271278
```
272279
```go

‎problems/0037.解数独.md‎

Lines changed: 53 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -756,6 +756,59 @@ object Solution {
756756
}
757757
}
758758
```
759+
### C#
760+
```csharp
761+
public class Solution
762+
{
763+
public void SolveSudoku(char[][] board)
764+
{
765+
BackTracking(board);
766+
}
767+
public bool BackTracking(char[][] board)
768+
{
769+
for (int i = 0; i < board.Length; i++)
770+
{
771+
for (int j = 0; j < board[0].Length; j++)
772+
{
773+
if (board[i][j] != '.') continue;
774+
for (char k = '1'; k <= '9'; k++)
775+
{
776+
if (IsValid(board, i, j, k))
777+
{
778+
board[i][j] = k;
779+
if (BackTracking(board)) return true;
780+
board[i][j] = '.';
781+
}
782+
}
783+
return false;
784+
}
785+
786+
}
787+
return true;
788+
}
789+
public bool IsValid(char[][] board, int row, int col, char val)
790+
{
791+
for (int i = 0; i < 9; i++)
792+
{
793+
if (board[i][col] == val) return false;
794+
}
795+
for (int i = 0; i < 9; i++)
796+
{
797+
if (board[row][i] == val) return false;
798+
}
799+
int startRow = (row / 3) * 3;
800+
int startCol = (col / 3) * 3;
801+
for (int i = startRow; i < startRow + 3; i++)
802+
{
803+
for (int j = startCol; j < startCol + 3; j++)
804+
{
805+
if (board[i][j] == val) return false;
806+
}
807+
}
808+
return true;
809+
}
810+
}
811+
```
759812

760813
<p align="center">
761814
<a href="https://programmercarl.com/other/kstar.html" target="_blank">

‎problems/0039.组合总和.md‎

Lines changed: 60 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -598,6 +598,66 @@ object Solution {
598598
}
599599
}
600600
```
601+
### C#
602+
```csharp
603+
public class Solution
604+
{
605+
public IList<IList<int>> res = new List<IList<int>>();
606+
public IList<int> path = new List<int>();
607+
public IList<IList<int>> CombinationSum(int[] candidates, int target)
608+
{
609+
BackTracking(candidates, target, 0, 0);
610+
return res;
611+
}
612+
public void BackTracking(int[] candidates, int target, int start, int sum)
613+
{
614+
if (sum > target) return;
615+
if (sum == target)
616+
{
617+
res.Add(new List<int>(path));
618+
return;
619+
}
620+
for (int i = start; i < candidates.Length; i++)
621+
{
622+
sum += candidates[i];
623+
path.Add(candidates[i]);
624+
BackTracking(candidates, target, i, sum);
625+
sum -= candidates[i];
626+
path.RemoveAt(path.Count - 1);
627+
}
628+
}
629+
}
630+
631+
// 剪枝优化
632+
public class Solution
633+
{
634+
public IList<IList<int>> res = new List<IList<int>>();
635+
public IList<int> path = new List<int>();
636+
public IList<IList<int>> CombinationSum(int[] candidates, int target)
637+
{
638+
Array.Sort(candidates);
639+
BackTracking(candidates, target, 0, 0);
640+
return res;
641+
}
642+
public void BackTracking(int[] candidates, int target, int start, int sum)
643+
{
644+
if (sum > target) return;
645+
if (sum == target)
646+
{
647+
res.Add(new List<int>(path));
648+
return;
649+
}
650+
for (int i = start; i < candidates.Length && sum + candidates[i] <= target; i++)
651+
{
652+
sum += candidates[i];
653+
path.Add(candidates[i]);
654+
BackTracking(candidates, target, i, sum);
655+
sum -= candidates[i];
656+
path.RemoveAt(path.Count - 1);
657+
}
658+
}
659+
}
660+
```
601661

602662

603663
<p align="center">

‎problems/0040.组合总和II.md‎

Lines changed: 33 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -773,7 +773,39 @@ object Solution {
773773
}
774774
}
775775
```
776-
776+
### C#
777+
```csharp
778+
public class Solution
779+
{
780+
public List<IList<int>> res = new List<IList<int>>();
781+
public List<int> path = new List<int>();
782+
public IList<IList<int>> CombinationSum2(int[] candidates, int target)
783+
{
784+
785+
Array.Sort(candidates);
786+
BackTracking(candidates, target, 0, 0);
787+
return res;
788+
}
789+
public void BackTracking(int[] candidates, int target, int start, int sum)
790+
{
791+
if (sum > target) return;
792+
if (sum == target)
793+
{
794+
res.Add(new List<int>(path));
795+
return;
796+
}
797+
for (int i = start; i < candidates.Length && sum + candidates[i] <= target; i++)
798+
{
799+
if (i > start && candidates[i] == candidates[i - 1]) continue;
800+
sum += candidates[i];
801+
path.Add(candidates[i]);
802+
BackTracking(candidates, target, i + 1, sum);
803+
sum -= candidates[i];
804+
path.RemoveAt(path.Count - 1);
805+
}
806+
}
807+
}
808+
```
777809
<p align="center">
778810
<a href="https://programmercarl.com/other/kstar.html" target="_blank">
779811
<img src="../pics/网站星球宣传海报.jpg" width="1000"/>

‎problems/0046.全排列.md‎

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -486,6 +486,37 @@ object Solution {
486486
}
487487
}
488488
```
489+
### C#
490+
```csharp
491+
public class Solution
492+
{
493+
public IList<IList<int>> res = new List<IList<int>>();
494+
public IList<int> path = new List<int>();
495+
public IList<IList<int>> Permute(int[] nums)
496+
{
497+
var used = new bool[nums.Length];
498+
BackTracking(nums, used);
499+
return res;
500+
}
501+
public void BackTracking(int[] nums, bool[] used)
502+
{
503+
if (path.Count == nums.Length)
504+
{
505+
res.Add(new List<int>(path));
506+
return;
507+
}
508+
for (int i = 0; i < nums.Length; i++)
509+
{
510+
if (used[i]) continue;
511+
used[i] = true;
512+
path.Add(nums[i]);
513+
BackTracking(nums, used);
514+
used[i] = false;
515+
path.RemoveAt(path.Count - 1);
516+
}
517+
}
518+
}
519+
```
489520

490521
<p align="center">
491522
<a href="https://programmercarl.com/other/kstar.html" target="_blank">

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