Merge pull request #297 from flames519/master

二叉树基础 JavaScript版本

problems/0102.二叉树的层序遍历.md

@@ -1100,6 +1100,276 @@ var levelOrder = function (root) {
 };
 ```
 
+> 二叉树的层序遍历（Javascript语言完全版） (迭代 + 递归)
+
+```js
+/**
+ * 102. 二叉树的层序遍历
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+
+// 迭代
+
+var levelOrder = function(root) {
+    const queue = [], res = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        const val = [];
+        while(len--) {
+            const node = queue.shift();
+            val.push(node.val);
+            node.left && queue.push(node.left);
+            node.right && queue.push(node.right);
+        }
+        res.push(val);
+    }
+    return res;
+};
+
+// 递归
+var levelOrder = function(root) {
+    const res = [];
+    function defs (root, i) {
+        if(!root) return;
+        if(!res[i]) res[i] = [];
+        res[i].push(root.val)
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return res;
+};
+
+
+/**
+ * 107. 二叉树的层序遍历 II
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+
+// 迭代
+
+var levelOrderBottom = function(root) {
+    const queue = [], res = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        const val = [];
+        while(len--) {
+            const node = queue.shift();
+            val.push(node.val);
+            node.left && queue.push(node.left);
+            node.right && queue.push(node.right);
+        }
+        res.push(val);
+    }
+    return res.reverse()
+};
+
+// 递归
+
+var levelOrderBottom = function(root) {
+    const res = [];
+    function defs (root, i) {
+        if(!root) return;
+        if(!res[i]) res[i] = [];
+        res[i].push(root.val);
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return res.reverse();
+};
+
+/**
+ * 199. 二叉树的右视图
+ * @param {TreeNode} root
+ * @return {number[]}
+ */
+
+// 迭代
+
+var rightSideView = function(root) {
+    const res = [], queue = [];
+    root && queue.push(root);
+    while(l = queue.length) {
+        while (l--) {
+            const {val, left, right} = queue.shift();
+            !l && res.push(val);
+            left && queue.push(left);
+            right && queue.push(right);
+        }
+    }
+    return res;
+};
+
+// 递归
+var rightSideView = function(root) {
+    const res = [];
+    function defs(root, i) {
+        if(!root) return;
+        res[i] = root.val;
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return res;
+};
+
+/**
+ * 637. 二叉树的层平均值
+ * @param {TreeNode} root
+ * @return {number[]}
+ */
+
+// 迭代
+var averageOfLevels = function(root) {
+    const queue = [], res = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        let sum = 0, l = len;
+        while(l--) {
+            const {val, left, right} = queue.shift();
+            sum += val;
+            left && queue.push(left);
+            right && queue.push(right);
+        }
+        res.push(sum/len);
+    }
+    return res;
+};
+
+// 递归
+var averageOfLevels = function(root) {
+    const resCount = [], res = [];
+    function defs(root, i) {
+        if(!root) return;
+        if(isNaN(res[i])) resCount[i] = res[i] = 0;
+        res[i] += root.val;
+        resCount[i]++;
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return res.map((val, i) => val / resCount[i]);
+};
+
+/**
+ * 515. 在每个树行中找最大值
+ * @param {TreeNode} root
+ * @return {number[]}
+ */
+
+// 迭代
+const MIN_G = Number.MIN_SAFE_INTEGER;
+var largestValues = function(root) {
+    const queue = [], res = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        let max = MIN_G;
+        while(len--) {
+            const {val, left, right} = queue.shift();
+            max = max > val ? max : val;
+            left && queue.push(left);
+            right && queue.push(right);
+        }
+        res.push(max);
+    }
+    return res;
+};
+
+// 递归
+var largestValues = function(root) {
+    const res = [];
+    function defs (root, i) {
+        if(!root) return;
+        if(isNaN(res[i])) res[i] = root.val;
+        res[i] = res[i] > root.val ? res[i] : root.val; 
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return res;
+};
+
+/**
+ * 429. N 叉树的层序遍历
+ * @param {Node|null} root
+ * @return {number[][]}
+ */
+
+// 迭代
+var levelOrder = function(root) {
+    const queue = [], res = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        const vals = [];
+        while(len--) {
+            const {val, children} = queue.shift();
+            vals.push(val);
+            for(const e of children) {
+                queue.push(e);
+            }
+        }
+        res.push(vals);
+    }
+    return res;
+};
+
+// 递归
+
+var levelOrder = function(root) {
+    const res = [];
+    function defs (root, i) {
+        if(!root) return;
+        if(!res[i]) res[i] = [];
+        res[i].push(root.val);
+        for(const e of root.children) {
+            defs(e, i + 1);
+        }
+    }
+    defs(root, 0);
+    return res;
+};
+
+/**
+ * 116. 填充每个节点的下一个右侧节点指针
+ * 117. 填充每个节点的下一个右侧节点指针 II
+ * @param {Node} root
+ * @return {Node}
+ */
+
+// 迭代
+var connect = function(root) {
+    const queue = [];
+    root && queue.push(root);
+    while(len = queue.length) {
+        while(len--) {
+            const node1 = queue.shift(), 
+                node2 = len ? queue[0] : null;
+            node1.next = node2;
+            node1.left && queue.push(node1.left);
+            node1.right && queue.push(node1.right);
+        }
+    }
+    return root;
+};
+
+// 递归
+var connect = function(root) {
+    const res = [];
+    function defs (root, i) {
+        if(!root) return;
+        if(res[i]) res[i].next = root; 
+        res[i] = root;
+        root.left && defs(root.left, i + 1);
+        root.right && defs(root.right, i + 1);
+    }
+    defs(root, 0);
+    return root;
+};
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)

problems/二叉树的统一迭代法.md

@@ -374,6 +374,86 @@ func postorderTraversal(root *TreeNode) []int {
 }
 ```
 
+javaScript:
+
+> 前序遍历统一迭代法
+
+```js
+
+// 前序遍历：中左右
+// 压栈顺序：右左中
+
+var preorderTraversal = function(root, res = []) {
+    const stack = [];
+    if (root) stack.push(root);
+    while(stack.length) {
+        const node = stack.pop();
+        if(!node) {
+            res.push(stack.pop().val);
+            continue;
+        }
+        if (node.right) stack.push(node.right); // 右
+        if (node.left) stack.push(node.left); // 左
+        stack.push(node); // 中
+        stack.push(null);
+    };
+    return res;
+};
+
+```
+
+> 中序遍历统一迭代法
+
+```js
+
+//  中序遍历：左中右
+//  压栈顺序：右中左
+ 
+var inorderTraversal = function(root, res = []) {
+    const stack = [];
+    if (root) stack.push(root);
+    while(stack.length) {
+        const node = stack.pop();
+        if(!node) {
+            res.push(stack.pop().val);
+            continue;
+        }
+        if (node.right) stack.push(node.right); // 右
+        stack.push(node); // 中
+        stack.push(null);
+        if (node.left) stack.push(node.left); // 左
+    };
+    return res;
+};
+
+```
+
+> 后序遍历统一迭代法
+
+```js
+
+// 后续遍历：左右中
+// 压栈顺序：中右左
+ 
+var postorderTraversal = function(root, res = []) {
+    const stack = [];
+    if (root) stack.push(root);
+    while(stack.length) {
+        const node = stack.pop();
+        if(!node) {
+            res.push(stack.pop().val);
+            continue;
+        }
+        stack.push(node); // 中
+        stack.push(null);
+        if (node.right) stack.push(node.right); // 右
+        if (node.left) stack.push(node.left); // 左
+    };
+    return res;
+};
+
+```
+
 
 
 -----------------------