5330. 分裂二叉树的最大乘积(dfs)

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    long long ans;
    long long sum;
    void dfs1(TreeNode* root){
        if(!root) return ;
        sum += root->val;
        dfs1(root->left);
        dfs1(root->right);
    }
    
    long long dfs2(TreeNode* root){
        if(!root) return 0;
        long long x = dfs2(root->left) + dfs2(root->right) + root->val;
        ans= max(ans, x * (sum - x));
        return x;
    }
    
    int maxProduct(TreeNode* root) {
        ans = 0;
        sum = 0;
        dfs1(root);
        dfs2(root);
        return ans % int(1e9+7);
    }
};