hdu1796容斥原理

这题是跟竹子compare时发现的，一直不会打代码，今天狠狠心学了学，打完了，可以加到模板里了。

/*

 * hdu1796/win.cpp

 * Created on: 2012-8-20

 * Author    : ben

 */

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cmath>

#include <ctime>

#include <iostream>

#include <algorithm>

#include <queue>

#include <set>

#include <map>

#include <stack>

#include <string>

#include <vector>

#include <deque>

#include <list>

#include <functional>

#include <numeric>

#include <cctype>

using namespace std;

const int MAXM = 15;

typedef long long LL;

int N, M, data[MAXM];

LL gcd(LL a, LL b) {

    LL r;

    while(b) {

        r = a % b;

        a = b, b = r;

    }

    return a;

}

LL getlcm(LL a, LL b) {

    LL c = gcd(a, b);

    return a / c * b;

}

/**

 * now当前点序号

 * count加入容斥的个数

 */

void dfs(int now, int count, LL lcm, LL &ans) {

    lcm = getlcm(lcm, data[now]);

    if(count % 2 == 0) {

        ans -= (N - 1) / lcm;

    }else {

        ans += (N - 1) / lcm;

    }

    for(int i = now + 1; i < M; i++) {

        dfs(i, count + 1, lcm, ans);

    }

}

LL work(int N, int M) {

    LL ans = 0;

    for(int i = 0; i < M; i++) {

        dfs(i, 1, data[i], ans);

    }

    return ans;

}

int main() {

#ifndef ONLINE_JUDGE

    freopen("data.in", "r", stdin);

#endif

    while(scanf("%d%d", &N, &M) == 2) {

        int m = 0;

        for(int i = 0; i < M; i++) {

            scanf("%d", &data[m]);

            if(data[m] > 0) {

                m++;

            }

        }

        M = m;

        printf("%I64d\n", work(N, M));

    }

    return 0;

}