12931 - Finding pairs - (2)

#include <stdio.h>
// basic counting way
long long int cnt[10005];
int main(){
    int x;
    int N;
    long long int total = 0;
    scanf("%d", &N);
    for(int i = 0; i < N; i++){
        // basically we just add the amount of pair we had b4, because position doesn't matter
        // only amount of numbers matters
        // 'streaming' algorithm
        // replace x, we do not need to use another array
        scanf("%d", &x);
        total += cnt[x]++;
    }
    printf("%lld\n", total);
    return 0;
}