codeforce543A_完全背包+滚动数组

题目链接：http://codeforces.com/contest/543/problem/A

题意：有n个程序员，m行代码，最多bug数为b

让这n个程序员完成这项任务，问有多少种分配方法，得到的答案取模mod

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define LL long long
using namespace std;

const int N = 502;
int bug[N], dp[2][N][N];
int main()
{
    int n, m, b;
    LL mod;
    while(~scanf("%d%d%d%I64d", &n, &m, &b, &mod))
    {
        LL res = 0;
        memset(dp, 0, sizeof(dp));
        for(int i = 0; i <= n; i++)
            dp[i % 2][0][0] = 1;
        for(int i = 1; i <= n; i++)
            scanf("%d", bug + i);
        for(int i = 1; i <= n; i++)//前i个人
        {
            for(int j = 1; j <= m; j++)//前i个人写j行代码
            {
                for(int k = 0; k <= b; k++)//前i个人写j行代码出k个bug时的分配方法个数
                {
                    if(k < bug[i]) 
                        dp[i % 2][j][k] = dp[(i - 1) % 2][j][k] % mod;
                    else
                        dp[i % 2][j][k] = (dp[(i - 1) % 2][j][k] + dp[i % 2][j - 1][k - bug[i]]) % mod;
                }
            }
        }
        for(int i = 0; i <= b; i++)
            res = (res + dp[n % 2][m][i]) % mod;
        printf("%I64d
", res);
    }
    return 0;
}