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Commit 30f0272

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Binary tree maximum path sum
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‎0124_binaryTreeMaximumPathSum.js

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/**
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* @typedef {Object} TreeNode
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* @description Definition for a binary tree node.
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* function TreeNode(val) {
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* this.val = val;
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* this.left = this.right = null;
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* }
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*/
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let max = Number.MIN_SAFE_INTEGER;
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const maxValue = node => {
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if (node === null) return 0;
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let leftValue = Math.max(maxValue(node.left), 0);
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let rightValue = Math.max(maxValue(node.right), 0);
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max = Math.max(max, node.val + leftValue + rightValue);
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return node.val + Math.max(leftValue, rightValue);
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};
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/**
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* @param {TreeNode} root Head of the binary tree.
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* @return {max} Maximum path sum.
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* @summary Binary Tree Maximum Path Sum {@link https://leetcode.com/problems/binary-tree-maximum-path-sum/}
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* @description Given a non-empty binary tree, find the maximum path sum
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* Space O(n) - where n is number of nodes.
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* Time O(k) - where k is height of tree.
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*/
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const maxPathSum = root => {
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maxValue(root);
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return max;
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};
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/**
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* @typedef {Object} TreeNode
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* @description Definition for a binary tree node.
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* function TreeNode(val) {
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* this.val = val;
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* this.left = this.right = null;
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* }
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*/
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/**
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* @summary Serialize and Deserialize Binary Tree {@link https://leetcode.com/problems/serialize-and-deserialize-binary-tree/solution/}
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* @description Write functions to serialize and deserialize binary tree.
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* Space O(n) - For both serialize and deserialize, we store every node.
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* Time O(n) - For both serialize and deserialize, we traverse every node.
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*/
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/**
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* Encodes a tree to a single string.
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*
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* @param {TreeNode} root
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* @return {string}
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*/
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const serialize = root => {
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const queue = [root];
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const result = [];
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while (queue.length) {
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const current = queue.shift();
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if (current === null) result.push('null');
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else {
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result.push(current.val);
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queue.push(current.left);
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queue.push(current.right);
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}
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}
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while (result[result.length - 1] === 'null') {
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result.pop();
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}
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return result.join(',');
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};
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/**
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* Decodes your encoded data to tree.
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*
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* @param {string} data
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* @return {TreeNode}
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*/
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const deserialize = string => {
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if (string === '') return null;
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const treeData = string.split(',');
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const root = new TreeNode(+treeData.shift());
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const queue = [root];
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while (queue.length) {
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const current = queue.shift();
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if (treeData.length) {
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const leftData = treeData.shift();
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if (leftData !== 'null') {
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const left = new TreeNode(+leftData);
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current.left = left;
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queue.push(current.left);
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}
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}
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if (treeData.length) {
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const rightData = treeData.shift();
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if (rightData !== 'null') {
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const right = new TreeNode(+rightData);
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current.right = right;
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queue.push(current.right);
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}
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}
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}
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return root;
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};

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