124 二叉树中的最大路径和

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xdhfe5/

cost: 33m57s

/**
 * 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 maxPathSum(TreeNode* root) {
        int sum = INT_MIN / 10;
        this->maxPathSum_(root, sum);
        return this->res;
    }

private:
    int maxPathSum_(TreeNode* root, int sum) {
        if (root == nullptr) {
            return INT_MIN / 10;
        }
        int v1 = this->maxPathSum_(root->left, sum + root->val);
        int v2 = this->maxPathSum_(root->right, sum + root->val);
        if (v1 < v2) {
            std::swap(v1, v2);
        }
        int maxChildSum = std::max(v1 + root->val, v2 + root->val);
        maxChildSum = std::max(maxChildSum, root->val);
        res = std::max(res, maxChildSum);
        res = std::max(res, sum);
        res = std::max(res, v1 + v2 + root->val);
        res = std::max(res, v1 + sum + root->val);
        res = std::max(res, sum + root->val);
        return maxChildSum;
    }
    int res = INT_MIN / 10;
};