124.cpp

/**
 * 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 res;
    int dfs(TreeNode* root){
        if(!root)
            return 0;
        auto left = dfs(root->left);
        auto right = dfs(root->right);
        res = max({res, left+root->val, right+root->val, left+right+root->val, root->val});
        return max({root->val, root->val+max(left,right)});
    }
    int maxPathSum(TreeNode* root) {
        res = INT_MIN;
        dfs(root);
        return res;
    }
};