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剑指Offer之Java算法习题精讲二叉树与N叉树

题目一 剑指Offer之Java算法习题精讲二叉树与N叉树
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【剑指Offer之Java算法习题精讲二叉树与N叉树】 解法

/** * Definition for a binary tree node. * public class TreeNode { *int val; *TreeNode left; *TreeNode right; *TreeNode() {} *TreeNode(int val) { this.val = val; } *TreeNode(int val, TreeNode left, TreeNode right) { *this.val = val; *this.left = left; *this.right = right; *} * } */class Solution {StringBuffer sb = new StringBuffer(); List list = new ArrayList(); public List binaryTreePaths(TreeNode root) {method(root); return list; }public void method(TreeNode root){if(root==null) return; int t = sb.length(); sb.append(root.val); if(root.left==null&&root.right==null){list.add(sb.toString()); }sb.append("->"); method(root.left); method(root.right); sb.delete(t, sb.length()); }}

题目二 剑指Offer之Java算法习题精讲二叉树与N叉树
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解法
/** * Definition for a binary tree node. * public class TreeNode { *int val; *TreeNode left; *TreeNode right; *TreeNode() {} *TreeNode(int val) { this.val = val; } *TreeNode(int val, TreeNode left, TreeNode right) { *this.val = val; *this.left = left; *this.right = right; *} * } */class Solution {int ans = 0; public int sumOfLeftLeaves(TreeNode root) {method(root,false); return ans; }public void method(TreeNode root,boolean flag){if(root==null) return; if(root.left==null&&root.right==null&&flag){ans+=root.val; return; }method(root.left,true); method(root.right,false); }}

题目三 剑指Offer之Java算法习题精讲二叉树与N叉树
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解法
/*// Definition for a Node.class Node {public int val; public List children; public Node() {}public Node(int _val) {val = _val; }public Node(int _val, List _children) {val = _val; children = _children; }}; */ class Solution {public int maxDepth(Node root) {if(root==null){return 0; }int maxChildDepth = 0; for(int i = 0; i
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