重拾算法之剑指Offier——树的子结构

2/22/2017来源:ASP.NET技巧人气:1868

树的子结构

题目描述 输入两棵二叉树A,B,判断B是不是A的子结构。(ps:我们约定空树不是任意一个树的子结构)

class TreeNode { int val = 0; TreeNode left = null; TreeNode right = null; public TreeNode(int val) { this.val = val; } } public class Solution { public boolean HasSubtree(TreeNode root1, TreeNode root2) { boolean flag = false; if (root1 != null && root2 != null){ if (root1.val == root2.val){ flag = doesTree1haveTree2(root1, root2); } if(flag == false){ flag = HasSubtree(root1.left, root2); } if(flag == false){ flag = HasSubtree(root1.right, root2); } } return flag; } public boolean doesTree1haveTree2(TreeNode root1, TreeNode root2){ if(root2 == null){ return true; } if(root1 == null || root1.val != root2.val){ return false; } return doesTree1haveTree2(root1.left,root2.left) && doesTree1haveTree2(root1.right,root2.right); } }