每周課金題
1973. Count Nodes Equal to Sum of Descendants
數有幾個node的value == 這個node的Descendants的sum
直接DFS+隨時計算答案
要注意會overflow 我送出去才知道 :(
long long helper(TreeNode* root, int* ans)
{
if(!root) {return 0;}
long long left_sum = helper(root->left, ans);
long long right_sum = helper(root->right, ans);
if((left_sum + right_sum) == root->val)
{
*ans += 1;
}
return left_sum + right_sum + (long long)root->val;
}
int equalToDescendants(TreeNode* root) {
int ans=0;
helper(root, &ans);
return ans;
}