competitive-programming/solved-uva/583.cpp at master · the-redback/competitive-programming · GitHub

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#include <bits/stdc++.h>
using namespace std;
bool pr[50001];

void sieve(int n) {
    memset(pr, 0, sizeof(pr));
    long i, j, k, l;
    pr[1] = 1;
    for (i = 4; i <= n; i += 2) pr[i] = 1;
    for (i = 3; i * i <= n; i += 2) {
        if (pr[i] == 0) {
            for (j = i * i; j <= n; j += 2 * i) pr[j] = 1;
        }
    }
}

int main() {
    vector<long long> v;
    sieve(50000);
    long long n, m;
    long long k;
    long long i;
    int j, t;
    while (scanf("%lld", &m)) {
        if (m == 0) return 0;
        if (m < 0) {
            n = m * -1;
        } else
            n = m;
        k = n;
        for (i = 2; i * i <= n; i++) {
            while (pr[i]) {
                i++;
            }
            while (k % i == 0) {
                k /= i;
                v.push_back(i);
            }
            if (k == 1) break;
        }
        printf("%lld = ", m);
        t = 0;
        if (m < 0) {
            printf("-1");
            t = 1;
        }
        for (i = 0; i < v.size(); i++) {
            if (t != 0) printf(" x ");
            printf("%lld", v[i]);
            t = 1;
        }
        if (k != 1) {
            if (t != 0) printf(" x ");
            printf("%lld", k);
        }
        printf("\n");
        v.clear();
    }
    return 0;
}