poj 2992 Divisors

2992 -- Divisors

　　筛素数，分解质因数。

代码如下：

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

typedef long long LL;
const int N = 444;
int prm[N >> 2], pn, pid[N], pv[N];
bool np[N];

void getPrm() {
    np[0] = np[1] = true;
    prm[pn = 0] = 2, pid[2] = pn++;
    for (int i = 3, tmp; i < N; i++, i++) {
        if (!np[i]) prm[pn] = i, pid[i] = pn++;
        for (int j = 0; j < pn; j++) {
            tmp = prm[j] * i;
            if (tmp >= N) break;
            np[tmp] = true;
            if (i % prm[j] == 0) break;
        }
    }
    pv[0] = pv[1] = 1, pv[2] = 2;
    for (int i = 2; i < N; i++, i++) pv[i] = 2;
    for (int i = 3; i < N; i++, i++) {
        if (!pv[i]) {
            for (int j = i; j < N; j += i) pv[j] = i;
        }
    }
//    cout << pn << endl;
//    for (int i = 0; i < 10; i++) cout << prm[i] << endl;
//    for (int i = 0; i < 10; i++) cout << pv[i] << endl;
}

const int M = 86;
LL dvs[N][N];
int tmp[M];

void PRE() {
    getPrm();
    dvs[0][0] = dvs[1][0] = dvs[1][1] = 1;
    for (int i = 2; i < N; i++) {
        for (int j = 0; j < M; j++) tmp[j] = 0;
        dvs[i][0] = 1;
        for (int j = 1; j <= i; j++) {
            int t = i - j + 1;
            while (t > 1) {
                tmp[pid[pv[t]]]++;
                t /= pv[t];
            }
            t = j;
            while (t > 1) {
                tmp[pid[pv[t]]]--;
                t /= pv[t];
            }
            dvs[i][j] = 1;
            for (int k = 0; k < M; k++) dvs[i][j] *= tmp[k] + 1;
//            if (i == 412 && j == 205) { for (int i = 0; i < M; i++) cout << tmp[i] << ' '; cout << endl; cout << dvs[i][j] << endl;}
        }
    }
//    puts("ok~");
}

int main() {
    int n, m;
    PRE();
//    cout << dvs[10][4] << endl;
    while (~scanf("%d%d", &n, &m)) printf("%lld
", dvs[n][m]);
    return 0;
}

——written by Lyon