Problem
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
即比较两个树是否一致。
Java 实现
package com.coderli.leetcode.algorithms.easy;
/**
* Given two binary trees, write a function to check if they are the same or not.
* <p>
* Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
* <p>
* <p>
* Example 1:
* <p>
* Input:<br>
* 1 1
* / \ / \
* 2 3 2 3
* <p>
* [1,2,3], [1,2,3]
* <p>
* Output: true
* <p></p>
* Example 2:
* <p>
* Input:
* 1 1
* / \
* 2 2
* <p>
* [1,2], [1,null,2]
* <p>
* Output: false
* <p>
* Example 3:
* <p>
* Input:
* 1 1
* / \ / \
* 2 1 1 2
* <p>
* [1,2,1], [1,1,2]
* <p>
* Output: false
*
* @author OneCoder 2017-11-10 23:01
*/
public class SameTree {
public static void main(String[] args) {
SameTree sameTree = new SameTree();
TreeNode oneRoot = sameTree.new TreeNode(1);
oneRoot.left = sameTree.new TreeNode(2);
TreeNode twoRoot = sameTree.new TreeNode(1);
oneRoot.right = sameTree.new TreeNode(2);
System.out.println(sameTree.isSameTree(oneRoot, twoRoot));
}
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);
}
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) {
val = x;
}
}
}
分析
超级简单题了。没什么好分析的。