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;
}