leetcode解题: Same Tree (100)

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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.

解法1：递归 / 分治

经典的二叉树的问题，用递归很容易解决。两个树相等首先是root的值要一样，然后左子树相等，右子树相等。终结条件是如果值不一样或者有一个root为空另一个不是空则结构不同。

C++

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/**
 * 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 false;
        }
        if (p != NULL && q == NULL) {
            return false;
        }
        if (p == NULL && q == NULL) {
            return true;
        }
        if (p-> val != q->val) {
            return false;
        }
        bool left = isSameTree(p->left, q->left);
        if (!left) return false;
        bool right = isSameTree(p->right, q->right);
        return right;
    }
};

Java

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