100. Same Tree

题目

 Given two binary trees, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical and the nodes have the same value.

Example 1:

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true

Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false

Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

解析

class Solution_100 {
public:
    bool isSameTree(TreeNode *p, TreeNode *q) {

        if (!p&&!q)
        {
            return true;
        }
        if (!p&&q)
        {
            return false;
        }
        if (p&&!q)
        {
            return false;
        }
        if (p->val!=q->val)
        {
            return false;
        }

        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }

    //非递归实现时：有NULL节点也入栈或者队列
    // ref：https://leetcode.com/problems/same-tree/discuss/32683
};

100. Same Tree