// you can use includes, for example: // #include <algorithm> // you can write to stdout for debugging purposes, e.g. // cout << "this is a debug message" << endl; int solution(int X, vector<int> &A) { // write your code in C++14 (g++ 6.2.0) vector<int>B(X,0); //loop thru the array A int sum = 0; for(int i = 0; i <= A.size(); i++) { //ignore values not in range 1 to x, and if position is -1, insert time from a->position is filled if(A[i]<=X && B[A[i]-1]==0) { sum++; B[A[i]-1]=1; } if(sum == X){return i;} } return -1; //loop thru the array B }