Merge branch 'youngyangyang04:master' into master

Author: Cwlrin

problems/0020.有效的括号.md

@@ -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>

problems/0028.实现strStr.md

@@ -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>

problems/0056.合并区间.md

@@ -96,7 +96,7 @@ public:
     vector<vector<int>> merge(vector<vector<int>>& intervals) {
         vector<vector<int>> result;
         if (intervals.size() == 0) return result;
-        // 排序的参数使用了lamda表达式
+        // 排序的参数使用了lambda表达式
         sort(intervals.begin(), intervals.end(), [](const vector<int>& a, const vector<int>& b){return a[0] < b[0];});
 
         result.push_back(intervals[0]);

problems/0151.翻转字符串里的单词.md

@@ -758,7 +758,63 @@ func reverseWord(_ s: inout [Character]) {
 }
 ```
 
+Scala:
+
+```scala
+object Solution {
+  def reverseWords(s: String): String = {
+    var sb = removeSpace(s) // 移除多余的空格
+    reverseString(sb, 0, sb.length - 1) // 翻转字符串
+    reverseEachWord(sb)
+    sb.mkString
+  }
+
+  // 移除多余的空格
+  def removeSpace(s: String): Array[Char] = {
+    var start = 0
+    var end = s.length - 1
+    // 移除字符串前面的空格
+    while (start < s.length && s(start) == ' ') start += 1
+    // 移除字符串后面的空格
+    while (end >= 0 && s(end) == ' ') end -= 1
+    var sb = "" // String
+    // 当start小于等于end的时候，执行添加操作
+    while (start <= end) {
+      var c = s(start)
+      // 当前字符不等于空，sb的最后一个字符不等于空的时候添加到sb
+      if (c != ' ' || sb(sb.length - 1) != ' ') {
+        sb ++= c.toString
+      }
+      start += 1 // 指针向右移动
+    }
+    sb.toArray
+  }
+
+  // 翻转字符串
+  def reverseString(s: Array[Char], start: Int, end: Int): Unit = {
+    var (left, right) = (start, end)
+    while (left < right) {
+      var tmp = s(left)
+      s(left) = s(right)
+      s(right) = tmp
+      left += 1
+      right -= 1
+    }
+  }
 
+  // 翻转每个单词
+  def reverseEachWord(s: Array[Char]): Unit = {
+    var i = 0
+    while (i < s.length) {
+      var j = i + 1
+      // 向后迭代寻找每个单词的坐标
+      while (j < s.length && s(j) != ' ') j += 1
+      reverseString(s, i, j - 1)  // 翻转每个单词
+      i = j + 1   // i往后更新
+    }
+  }
+}
+```
 
 
 

problems/0203.移除链表元素.md

@@ -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：

problems/0225.用队列实现栈.md

@@ -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>

problems/0232.用栈实现队列.md

@@ -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>

problems/0404.左叶子之和.md

@@ -336,8 +336,8 @@ var sumOfLeftLeaves = function(root) {
         if(node===null){
             return 0;
         }
-        let leftValue = sumOfLeftLeaves(node.left);
-        let rightValue = sumOfLeftLeaves(node.right);
+        let leftValue = nodesSum(node.left);
+        let rightValue = nodesSum(node.right);
         // 3. 单层递归逻辑
         let midValue = 0;
         if(node.left&&node.left.left===null&&node.left.right===null){