第21天

比较，如果从这一分支出发总和更大，修改tmp，若分支和小于零，放弃

int tmp = INT_MIN;

int maxPathSum(TreeNode* root) {
	getdfs(root);
	return tmp;
}

int getdfs(TreeNode* node){
    if(node == NULL) return 0;
    int left = max(getdfs(node->left),0);
    int right = max(getdfs(node->right),0);
    int size = left + right + node->val;
    tmp = tmp > size ? tmp: size;
    return (right > left ? right:left) + node->val;
}