LeetCode/124.cpp at main · vys1n/LeetCode · GitHub

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#include <algorithm>
#include <bits/stdc++.h>
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:
    int maxPathSum(TreeNode* root) {
        int res = root->val;
        dfs(root, res);
        return res;
    }

private:
    int dfs(TreeNode* root, int& res) {
        if (!root) return 0;

        int leftMax = max(dfs(root->left, res), 0);
        int rightMax = max(dfs(root->right, res), 0);

        res = max(res, root->val + leftMax + rightMax);

        return root->val + max(leftMax, rightMax);
    }
};