The correct, optimal and working solution for programming question missing-numbers on hackerrank

/* * Author: Arpit Bhayani * https://arpitbhayani.me */ #include <cmath> #include <cstdio> #include <cstdlib> #include <climits> #include <deque> #include <iostream> #include <list> #include <limits> #include <map> #include <queue> #include <set> #include <stack> #include <vector> #define ll long long #define MIN(a, b) a < b ? a : b #define MAX(a, b) a > b ? a : b using namespace std; int readline(char *str) { int i = 0; char ch; while((ch = getchar()) != '\n') { str[i++] = ch; } str[i] = '\0'; return i; } int h1[220]; int h2[220]; int main(int argc, char *argv[]) { int n, m, x; int base; scanf("%d", &n); for(int i = 0; i < n; i++) { scanf("%d", &x); if(i == 0) { base = x; } h1[100 + (x - base)]++; } scanf("%d", &m); for(int i = 0; i < m; i++) { scanf("%d", &x); h2[100 + (x - base)]++; } vector<int> y; for(int i = 0 ; i < 220; i++) { int d = (h2[i] - h1[i]); if(d > 0) { y.push_back(i + base - 100); } } for(vector<int>::iterator itr = y.begin(); itr != y.end(); itr++) { cout << *itr << " "; } cout << endl; return 0; }