题解 | #树的子结构#

import java.util.*;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        if(root1 == null || root2 == null){
            return false;
        }
	  //如果两个根节点相等，则进入下个函数判断孩子节点
	  //否则就递归，用根节点的左右孩子节点进行比较
        return isSub(root1,root2)||HasSubtree(root1.left,root2)||HasSubtree(root1.right,root2);
    }
    public boolean isSub(TreeNode root1,TreeNode root2){
        if(root2 == null){
            return true;
        }
        if(root1 == null){
            return false;
        }
        if(root1.val != root2.val){
            return false;
        }
        return isSub(root1.right,root2.right)&&isSub(root1.left,root2.left);
    }
}