LeetCode-E-Same Tree

題目

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

遞歸實現：

• 均爲null，返回true
• 一個null，一個非null，返回false
• 均非null，但值不相等，返回false
• 均非null，且值相等，返回sameTree(左右子樹)

實現

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