leetcode 100.相同的树

package com.example.lettcode.dailyexercises;

/**
 * @Class IsSameTree
 * @Description 100.相同的树
 * 给定两个二叉树，编写一个函数来检验它们是否相同。
 * 如果两个树在结构上相同，并且节点具有相同的值，则认为它们是相同的。
 * <p>
 * 示例 1:
 * 输入:
 * 1         1
 * /        / 
 * 2   3     2   3
 * <p>
 * [1,2,3],   [1,2,3]
 * <p>
 * 输出: true
 * <p>
 * 示例 2:
 * <p>
 * 输入:
 * 1          1
 * /           
 * 2             2
 * <p>
 * [1,2],     [1,null,2]
 * <p>
 * 输出: false
 * <p>
 * 示例 3:
 * 输入:
 * 1         1
 * /        / 
 * 2   1     1   2
 * <p>
 * [1,2,1],   [1,1,2]
 * <p>
 * 输出: false
 * @Author
 * @Date 2020/8/7
 **/
public class IsSameTree {
    static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

    public static boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null) return q == null;
        if (q == null) return p == null;
        if (p.val != q.val) return false;
        boolean resL = isSameTree(p.left, q.left);
        boolean resR = isSameTree(p.right, q.right);
        return resL && resR;
    }

    public static void main(String[] args) {
        // [1,2,3],   [1,2,3]
        TreeNode rootP = new TreeNode(1);
        TreeNode treeNode2 = new TreeNode(2);
        TreeNode treeNode3 = new TreeNode(3);
        rootP.left = treeNode2;
        rootP.right = treeNode3;
        TreeNode rootQ = new TreeNode(1);
        treeNode2 = new TreeNode(2);
        treeNode3 = new TreeNode(3);
        rootQ.left = treeNode2;
        rootQ.right = treeNode3;
        boolean ans = isSameTree(rootP, rootQ);
        System.out.println("IsSameTree demo01 result:" + ans);

        // [1,2],     [1,null,2]
        rootP = new TreeNode(1);
        treeNode2 = new TreeNode(2);
        rootP.left = treeNode2;
        rootQ = new TreeNode(1);
        treeNode2 = new TreeNode(2);
        rootQ.right = treeNode2;
        ans = isSameTree(rootP, rootQ);
        System.out.println("IsSameTree demo02 result:" + ans);

        //[1,2,1],   [1,1,2]
        rootP = new TreeNode(1);
        treeNode2 = new TreeNode(2);
        treeNode3 = new TreeNode(1);
        rootP.left = treeNode2;
        rootP.right = treeNode3;
        rootQ = new TreeNode(1);
        treeNode2 = new TreeNode(1);
        treeNode3 = new TreeNode(2);
        rootQ.left = treeNode2;
        rootQ.right = treeNode3;
        ans = isSameTree(rootP, rootQ);
        System.out.println("IsSameTree demo03 result:" + ans);
    }
}