100. Same Tree

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.

一刷
题解：用recursion做，思路很简单

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

二刷
recursion

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if(p == null && q == null) return true;
        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); 
    }
}