标签：tree false top ural node blog etc rally leetcode
Given two binary trees, write a function to check if they are equal or not.
Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
首先是递归版本:
bool isSameTree(TreeNode* p, TreeNode* q) {//递归 if (p == NULL && q == NULL) return true; if (p == NULL && q != NULL || p != NULL && q == NULL || q->val != p->val) return false; return isSameTree(p->left, q->left) && isSameTree(p->right,q->right); }
运行效率：
对比一下非递归版本：
bool isSameTree2(TreeNode* p, TreeNode* q) {//先序非递归 stack<TreeNode*>st1, st2; if (p != NULL)st1.push(p); if (q!= NULL)st2.push(q); TreeNode* ptemp; TreeNode* qtemp; while (!st1.empty() && !st2.empty()) { ptemp = st1.top(); qtemp = st2.top(); if (ptemp->val != qtemp->val) return false; st1.pop(); st2.pop(); if (ptemp->right != NULL) st1.push(ptemp->right); if (qtemp->right != NULL) st2.push(qtemp->right); if (st1.size() != st2.size()) return false;//比较两个栈的大小 if (ptemp->left != NULL) st1.push(ptemp->left); if (qtemp->left != NULL) st2.push(qtemp->left); if (st1.size() != st2.size()) return false;//比较两个栈的大小 } return (st1.size() == st2.size()); }
运行效率：
可见，非递归确实效率要高一些。
标签：tree false top ural node blog etc rally leetcode
原文地址：http://www.cnblogs.com/hellowooorld/p/6442312.html
