No.265 - [1145] Binary Tree Coloring Game - 树遍历

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本文探讨了在LeetCode问题1145中，如何有效地处理边界样例，深入解析了二叉树着色游戏的DFS算法，并提供了解决边界情况的优化策略。通过递归函数dfsSum和dfs，分析了赢得游戏的关键节点条件。

边界样例有点多

/*
 * @lc app=leetcode id=1145 lang=cpp
 *
 * [1145] Binary Tree Coloring Game
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * 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:
    int dfsSum(TreeNode* now){
        if(now == NULL) return 0;
        int num = 0;
        num += dfsSum(now->left);
        num += dfsSum(now->right);
        return num + 1;
    }
    bool dfs(TreeNode* now, int val, int all) {
        if(now->val == val) {
            int xRoot = dfsSum(now);
            int xLeft = dfsSum(now->left);
            int xRight = dfsSum(now->right);
            if(xRoot <= all/2 || xLeft > all - xRoot + xRight + 1 || xRight > all - xRoot + xLeft + 1) {
                return true;
            }
            return false;
        }
        bool ans = false ;
        if(now->left != NULL){
            ans = ans || dfs(now->left, val, all);
        }
        if(now->right != NULL){
            ans = ans || dfs(now->right, val, all);
        }
        return ans;
    }
    bool btreeGameWinningMove(TreeNode* root, int n, int x) {
        return dfs(root, x, n);
    }
};
// @lc code=end