codeforce Gym 101102A Coins （01背包变形）

Posted 2020-08-13 icode-xiaohu

　　01背包变形，注意dp过程的时候就需要取膜，否则会出错。

　　代码如下：

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXW 15005
#define N 155
#define LL long long
#define MOD 1000000007
int w1[N],w2[N];
LL dp1[MAXW],dp2[MAXW];
int main()
{
//    freopen("A.in.cpp","r",stdin);
    int t,n,m,k,W,s,e;
    int sum1,sum2;
    LL ans;
    cin>>t;
    while(t--)
    {
        cin>>n>>m>>k>>W;
        sum1 = sum2 = 0;
        for(int i = 0; i < n; i++)
        {
            cin>>w1[i];
            sum1 += w1[i];
        }
        for(int i = 0; i < m; i++)
        {
            cin>>w2[i];
            sum2 += w2[i];
        }
        memset(dp1,0,sizeof(dp1));
        memset(dp2,0,sizeof(dp2));
        dp1[0] = dp2[0] = 1;
        for(int i = 0; i < n; i++)
        {
            for(int j = sum1; j >= w1[i]; j--)
            {
                dp1[j] = (dp1[j]%MOD + dp1[j-w1[i]]%MOD)%MOD;///没有mod就wa
            }
        }
        for(int i = 0; i < m; i++)
        {
            for(int j = sum2; j >= w2[i]; j--)
            {
                dp2[j] = (dp2[j]%MOD + dp2[j-w2[i]]%MOD)%MOD;
            }
        }
        if((W-k)%2 != 0) s = (W-k)/2+1;
        else s = (W-k)/2;
        e = W-s;
        ans = 0;
        for(int i = s; i <= e; i++)
        {
            ans = (((dp1[i]%MOD)*(dp2[W-i]%MOD))%MOD + ans%MOD) % MOD;
        }
        cout<<ans<<endl;
    }
    return 0;
}