leetcode+ 二叉树最大路径和，不一定要经过root,DFS

点击打开链接

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
class Solution {
public:
    int ans = 0;
    int dfs(TreeNode* root)
    {
        if(!root) return 0;
        int left = max(0, dfs(root->left));
        int right = max(0, dfs(root->right));
        ans = max(ans, left+root->val+right);
        return root->val+max(left, right);
    }
    int maxPathSum(TreeNode* root) {
        ans = INT_MIN;
        dfs(root);
        return ans;
    }
};