Submission

Score: 100

User: loop

Problemset: Twin, Cousin, and Sexy Prime

Language: cpp

Time: 0.317 second

Submitted On: 2026-10-10 18:33:04

#include <cstdio>
#include <vector>
using namespace std;

// Count primes p in [L, U] whose partner p-g or p+g (g = 2, 4, 6) is also prime; the partner may lie outside the range.
int main() {
    int L, U;
    scanf("%d %d", &L, &U);
    int top = U + 6;
    vector<bool> comp(top + 1, false);
    comp[0] = comp[1] = true;
    for (long long i = 2; i * i <= top; i++)
        if (!comp[i])
            for (long long j = i * i; j <= top; j += i) comp[j] = true;
    int cnt[3] = {0, 0, 0};
    for (int p = L; p <= U; p++) {
        if (comp[p]) continue;
        for (int k = 0; k < 3; k++) {
            int g = 2 * (k + 1);
            if ((p - g >= 2 && !comp[p - g]) || !comp[p + g]) cnt[k]++;
        }
    }
    printf("%d\n%d\n%d\n", cnt[0], cnt[1], cnt[2]);
    return 0;
}