UVa 12239 - Bingo (try all 90^2 pairs, see if all numbers in [0..N] are there)

Link:https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=244&page=show_problem&problem=3391
Sol:

#include <cstdio>
	#include <cmath>
	#include <set>
	using namespace std;
	int main() {
	int n, b, x[100];
	while (scanf("%d %d", &n, &b), n || b) {
	set<int> checker;
	for (int i = 0; i < b; i++) {
	scanf("%d", &x[i]);
	}
	for (int i = 0; i < b; i++) {
	for (int j = i; j < b; j++) {
	int d = abs(x[i] - x[j]);
	if (d <= n)
	checker.insert(d);
	}
	}
	if (checker.size() == n + 1)
	printf("Y\n");
	else
	printf("N\n");
	}
	return 0;
	}