[pull] master from youngyangyang04:master #10

Original file line number	Diff line number	Diff line change
Expand Up		@@ -400,6 +400,27 @@ bool isValid(char * s){
		return !stackTop;
		}
		```

	Scala:
	```scala
	object Solution {
	import scala.collection.mutable
	def isValid(s: String): Boolean = {
	if(s.length % 2 != 0) return false // 如果字符串长度是奇数直接返回false
	val stack = mutable.Stack[Char]()
	// 循环遍历字符串
	for (i <- s.indices) {
	val c = s(i)
	if (c == '(' \|\| c == '[' \|\| c == '{') stack.push(c)
	else if(stack.isEmpty) return false // 如果没有(、[、{则直接返回false
	// 以下三种情况,不满足则直接返回false
	else if(c==')' && stack.pop() != '(') return false
	else if(c==']' && stack.pop() != '[') return false
	else if(c=='}' && stack.pop() != '{') return false
	}
	// 如果为空则正确匹配,否则还有余孽就不匹配
	stack.isEmpty
	}
	}
	```
		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

75 changes: 75 additions & 0 deletions problems/0028.实现strStr.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -1166,5 +1166,80 @@ func strStr(_ haystack: String, _ needle: String) -> Int {

		```

	PHP:

	> 前缀表统一减一
	```php
	function strStr($haystack, $needle) {
	if (strlen($needle) == 0) return 0;
	$next= [];
	$this->getNext($next,$needle);

	$j = -1;
	for ($i = 0;$i < strlen($haystack); $i++) { // 注意i就从0开始
	while($j >= 0 && $haystack[$i] != $needle[$j + 1]) {
	$j = $next[$j];
	}
	if ($haystack[$i] == $needle[$j + 1]) {
	$j++;
	}
	if ($j == (strlen($needle) - 1) ) {
	return ($i - strlen($needle) + 1);
	}
	}
	return -1;
	}

	function getNext(&$next, $s){
	$j = -1;
	$next[0] = $j;
	for($i = 1; $i < strlen($s); $i++) { // 注意i从1开始
	while ($j >= 0 && $s[$i] != $s[$j + 1]) {
	$j = $next[$j];
	}
	if ($s[$i] == $s[$j + 1]) {
	$j++;
	}
	$next[$i] = $j;
	}
	}
	```

	> 前缀表统一不减一
	```php
	function strStr($haystack, $needle) {
	if (strlen($needle) == 0) return 0;
	$next= [];
	$this->getNext($next,$needle);

	$j = 0;
	for ($i = 0;$i < strlen($haystack); $i++) { // 注意i就从0开始
	while($j > 0 && $haystack[$i] != $needle[$j]) {
	$j = $next[$j-1];
	}
	if ($haystack[$i] == $needle[$j]) {
	$j++;
	}
	if ($j == strlen($needle)) {
	return ($i - strlen($needle) + 1);
	}
	}
	return -1;
	}

	function getNext(&$next, $s){
	$j = 0;
	$next[0] = $j;
	for($i = 1; $i < strlen($s); $i++) { // 注意i从1开始
	while ($j > 0 && $s[$i] != $s[$j]) {
	$j = $next[$j-1];
	}
	if ($s[$i] == $s[$j]) {
	$j++;
	}
	$next[$i] = $j;
	}
	}
	```
		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

21 changes: 21 additions & 0 deletions problems/0203.移除链表元素.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -266,6 +266,27 @@ public ListNode removeElements(ListNode head, int val) {
		}
		return head;
		}
	/**
	* 不添加虚拟节点and pre Node方式
	* 时间复杂度 O(n)
	* 空间复杂度 O(1)
	* @param head
	* @param val
	* @return
	*/
	public ListNode removeElements(ListNode head, int val) {
	while(head!=null && head.val==val){
	head = head.next;
	}
	ListNode curr = head;
	while(curr!=null){
	while(curr.next!=null && curr.next.val == val){
	curr.next = curr.next.next;
	}
	curr = curr.next;
	}
	return head;
	}
		```

		Python:
Expand Down

83 changes: 83 additions & 0 deletions problems/0225.用队列实现栈.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -815,6 +815,89 @@ class MyStack {
		}
		}
		```
	Scala:

	使用两个队列模拟栈:
	```scala
	import scala.collection.mutable

	class MyStack() {

	val queue1 = new mutable.Queue[Int]()
	val queue2 = new mutable.Queue[Int]()

	def push(x: Int) {
	queue1.enqueue(x)
	}

	def pop(): Int = {
	var size = queue1.size
	// 将queue1中的每个元素都移动到queue2
	for (i <- 0 until size - 1) {
	queue2.enqueue(queue1.dequeue())
	}
	var res = queue1.dequeue()
	// 再将queue2中的每个元素都移动到queue1
	while (!queue2.isEmpty) {
	queue1.enqueue(queue2.dequeue())
	}
	res
	}

	def top(): Int = {
	var size = queue1.size
	for (i <- 0 until size - 1) {
	queue2.enqueue(queue1.dequeue())
	}
	var res = queue1.dequeue()
	while (!queue2.isEmpty) {
	queue1.enqueue(queue2.dequeue())
	}
	// 最终还需要把res送进queue1
	queue1.enqueue(res)
	res
	}

	def empty(): Boolean = {
	queue1.isEmpty
	}
	}
	```
	使用一个队列模拟:
	```scala
	import scala.collection.mutable

	class MyStack() {

	val queue = new mutable.Queue[Int]()

	def push(x: Int) {
	queue.enqueue(x)
	}

	def pop(): Int = {
	var size = queue.size
	for (i <- 0 until size - 1) {
	queue.enqueue(queue.head) // 把头添到队列最后
	queue.dequeue() // 再出队
	}
	queue.dequeue()
	}

	def top(): Int = {
	var size = queue.size
	var res = 0
	for (i <- 0 until size) {
	queue.enqueue(queue.head) // 把头添到队列最后
	res = queue.dequeue() // 再出队
	}
	res
	}

	def empty(): Boolean = {
	queue.isEmpty
	}
	}
	```
		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

41 changes: 40 additions & 1 deletion problems/0232.用栈实现队列.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -495,6 +495,45 @@ void myQueueFree(MyQueue* obj) {
		obj->stackOutTop = 0;
		}
		```

	Scala:
	```scala
	class MyQueue() {
	import scala.collection.mutable
	val stackIn = mutable.Stack[Int]() // 负责出栈
	val stackOut = mutable.Stack[Int]() // 负责入栈

	// 添加元素
	def push(x: Int) {
	stackIn.push(x)
	}

	// 复用代码,如果stackOut为空就把stackIn的所有元素都压入StackOut
	def dumpStackIn(): Unit = {
	if (!stackOut.isEmpty) return
	while (!stackIn.isEmpty) {
	stackOut.push(stackIn.pop())
	}
	}

	// 弹出元素
	def pop(): Int = {
	dumpStackIn()
	stackOut.pop()
	}

	// 获取队头
	def peek(): Int = {
	dumpStackIn()
	val res: Int = stackOut.pop()
	stackOut.push(res)
	res
	}

	// 判断是否为空
	def empty(): Boolean = {
	stackIn.isEmpty && stackOut.isEmpty
	}
	}
	```
		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

4 changes: 2 additions & 2 deletions problems/0739.每日温度.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -193,7 +193,7 @@ class Solution {
		否则的话,可以直接入栈。
		注意,单调栈里加入的元素是下标。
		*/
	Stack<Integer>stack=new Stack<>();
	Deque<Integer>stack=new LinkedList<>();
		stack.push(0);
		for(int i=1;i<lens;i++){

Expand All		@@ -217,7 +217,7 @@ class Solution {
		public int[] dailyTemperatures(int[] temperatures) {
		int lens=temperatures.length;
		int []res=new int[lens];
	Stack<Integer>stack=new Stack<>();
	Deque<Integer>stack=new LinkedList<>();
		for(int i=0;i<lens;i++){

		while(!stack.isEmpty()&&temperatures[i]>temperatures[stack.peek()]){
Expand Down

23 changes: 22 additions & 1 deletion problems/1047.删除字符串中的所有相邻重复项.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -374,6 +374,27 @@ func removeDuplicates(_ s: String) -> String {
		return String(stack)
		}
		```

	Scala:
	```scala
	object Solution {
	import scala.collection.mutable
	def removeDuplicates(s: String): String = {
	var stack = mutable.Stack[Int]()
	var str = "" // 保存最终结果
	for (i <- s.indices) {
	var tmp = s(i)
	// 如果栈非空并且栈顶元素等于当前字符,那么删掉栈顶和字符串最后一个元素
	if (!stack.isEmpty && tmp == stack.head) {
	str = str.take(str.length - 1)
	stack.pop()
	} else {
	stack.push(tmp)
	str += tmp
	}
	}
	str
	}
	}
	```
		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

23 changes: 23 additions & 0 deletions problems/剑指Offer58-II.左旋转字符串.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -290,6 +290,28 @@ func reverseString(_ s: inout [Character], startIndex: Int, endIndex: Int) {
		}
		```


	### PHP

	```php
	function reverseLeftWords($s, $n) {
	$this->reverse($s,0,$n-1); //反转区间为前n的子串
	$this->reverse($s,$n,strlen($s)-1); //反转区间为n到末尾的子串
	$this->reverse($s,0,strlen($s)-1); //反转整个字符串
	return $s;
	}

	// 按指定进行翻转【array、string都可】
	function reverse(&$s, $start, $end) {
	for ($i = $start, $j = $end; $i < $j; $i++, $j--) {
	$tmp = $s[$i];
	$s[$i] = $s[$j];
	$s[$j] = $tmp;
	}
	}
	```


		Scala:

		```scala
Expand Down Expand Up		@@ -322,5 +344,6 @@ object Solution {




		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

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