题解 | 二叉树中的最大路径和

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <stdexcept>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型
     */
    int ans = INT_MIN;

    int dfs(TreeNode* root) {
        if (!root) return 0;
        int l_num = max(0, dfs(root->left));
        int r_num = max(0, dfs(root->right));
        
        int sum = root->val + l_num + r_num;
        ans = max(ans , sum);

        return root->val + max(l_num, r_num);
    }


    int maxPathSum(TreeNode* root) {
        if (!root) return 0;
        dfs(root);
        return ans;
    }
};