100. Same Tree (Tree;DFS)

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.

思路：如果两个树相同，那么他们的左子树、右子树必定也相同=>递归=>可用前序、中序或后续遍历。

以下用的是前序遍历，先处理根节点。

/*** Definition for a binary tree node.* struct TreeNode {*int val;*TreeNode *left;*TreeNode *right;*TreeNode(int x) : val(x), left(NULL), right(NULL) {}* };*/class Solution {public:bool isSameTree(TreeNode* p, TreeNode* q) {if (p==NULL && q==NULL) return true;else if(p!=NULL && q!=NULL){ if(p->val != q->val) return false;}else return false;if (!isSameTree(p->left,q->left)) return false;if (!isSameTree(p->right,q->right)) return false;return true;}};