5 POJ 3132 Sum of Different Primes

dp[j][k]表示用j个质数表示k这个值得方法数。

一个质数只能用一次，类似01背包。

#include<cstdio>
#include<cstring>
const int maxn=1130;
int pri[maxn+10],dp[20][maxn+10];
void init()
{
    int i,j;
    for(i=0;i<=maxn;i++) pri[i]=1;
    pri[0]=pri[1]=0;
    for(i=2;i<=maxn;i++)
    {
        if(!pri[i]) continue;
        for(j=i+i;j<=maxn;j+=i)
            pri[j]=0;
    }
}
int main()
{
    init();
    int i,j,k,m,n;
    while(scanf("%d%d",&n,&m)&&(n||m))
    {
        memset(dp,0,sizeof dp);
        dp[0][0]=1;
        for(i=2;i<=n;i++)
        {
            if(!pri[i]) continue;
            for(k=n;k>=i;k--)
                for(j=m;j>0;j--)
                    dp[j][k]+=dp[j-1][k-i];
        }
        printf("%d\n",dp[m][n]);
    }
    return 0;
}

时间： 2024-10-10 00:53:10

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