#include using namespace std; class Solution { public: int threeSumMulti(vector &arr, int target) { int n = arr.size(), mod = 1e9 + 7, ans = 0; unordered_map m; for (int i = 0; i < n; i++) { ans = (ans + m[target - arr[i]]) % mod; for (int j = 0; j < i; j++) m[arr[i] + arr[j]]++; } return ans; } }; int main() {}