1 class Solution 2 { 3 private: 4 int hashList[102]; 5 public: 6 long long int get(long long int n,long long int m) 7 { 8 if(m==1) 9 return n; 10 else if(m==2) 11 return (n*(n-1))/2; 12 else if(m==3) 13 return (n*(n-1)*(n-2))/6; 14 } 15 int threeSumMulti(vector<int>& A, int target) 16 { 17 memset(hashList,0,sizeof(hashList)); 18 19 for(auto d:A) 20 hashList[d] ++; 21 22 long long int result = 0; 23 for(int i = 0; i <= target&&i<=100; i ++) 24 { 25 if(hashList[i]>=3 && 3*i==target) 26 { 27 result += get(hashList[i],3); 28 result %= 1000000007; 29 } 30 if(2*i<target && hashList[i]>=2) 31 { 32 if(target-2*i > i && target-2*i <= 100 && hashList[target-2*i]) 33 { 34 result += hashList[target-2*i]*get(hashList[i],2); 35 result %= 1000000007; 36 // cout << i << " " << i << " " << target-2*i << endl; 37 } 38 } 39 if(hashList[i]) 40 { 41 for(int j = i+1; j <= target && j<=100; j ++) 42 { 43 if(hashList[j]>=2 && 2*j+i==target) 44 { 45 result += hashList[i]*get(hashList[j],2); 46 result %= 1000000007; 47 // cout << i << " " << j << " " << j << endl; 48 } 49 if(hashList[j]) 50 { 51 if(target-i-j > j && target-i-j <= 100 && hashList[target-i-j]) 52 { 53 result += hashList[i]*hashList[j]*hashList[target-i-j]; 54 result %= 1000000007; 55 // cout << i << " " << j << " " << target-i-j << endl; 56 } 57 } 58 } 59 } 60 } 61 result %= 1000000007; 62 return (int)result; 63 } 64 };