leetcode - 100 same tree

发表于 | 分类于 |

级别： easy

方法： 递归层序遍历

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//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
// 
//

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

        // 递归层序遍历即可

        // 1、递归的出口
        if (null == p && null == q) {
            return true;
        }

        if(null ==p && null !=q) {
            return false;
        }

        if(null != p && null ==q) {
            return false;
        }

        // 2、递归的递进条件
        if( p.val != q.val) {
            return false;
        }

        boolean isLeftSame =  isSameTree(p.left,q.left);
        if(!isLeftSame) {
            return false;
        }

        boolean isRightSame =  isSameTree(p.right,q.right);
        return isLeftSame && isRightSame;
    }
}