【LeetCode-572 | 另一棵树的子树】

题目.jpg 题目.jpg 题目.jpg 题目.jpg

#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>

using namespace std;


struct TreeNode{
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(): val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x): val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode* left, TreeNode* right): val(x), left(left), right(right) {}
};



class Solution {
public:
    // 1.确定递归函数入参及返回值
    bool compare(TreeNode* tr1, TreeNode* tr2) {
        // 2.确定函数的递归终止条件
        if(tr1 == nullptr && tr2 == nullptr) return true;
        else if(tr1 == nullptr && tr2 != nullptr) return false;
        else if(tr1 != nullptr && tr2 == nullptr) return false;
        else if(tr1->val != tr2->val) return false;
        // 3.确定单层递归逻辑
        else return compare(tr1->left, tr2->left) && compare(tr1->right, tr2->right);
    }

    bool isSubTree(TreeNode* root, TreeNode* subRoot) {
        if(root == nullptr) return false;
        if(subRoot == nullptr) return true;
        // 符合subRoot是root子树的三种情况(满足其中之一即可)：两棵树完全相同；SubRoot为root的左子树；SubRoot为root的右子树
        return compare(root, subRoot) || isSubTree(root->left, subRoot) || isSubTree(root->right, subRoot);
    }
};