BZOJ.2287.[POJ Challenge]消失之物(退背包)

BZOJ
洛谷

退背包。和原DP的递推一样，再减去一次递推就行了。

f[i][j] = f[i-1][j-w[i]] + f[i-1][j]
f[i-1][j] = f[i][j] - f[i-1][j-w[i]]

//1136kb    56ms
#include <cstdio>
#include <cctype>
#include <cstring>
#define gc() getchar()
const int N=2005;

int w[N],f[N],g[N];

inline int read()
{
    int now=0;register char c=gc();
    for(;!isdigit(c);c=gc());
    for(;isdigit(c);now=now*10+c-'0',c=gc());
    return now;
}

int main()
{
    int n=read(),m=read();
    for(int i=1; i<=n; ++i) w[i]=read();
    f[0]=1;
    for(int i=1; i<=n; ++i)
        for(int j=m,wi=w[i]; j>=wi; --j) (f[j]+=f[j-wi])%=10;
    for(int i=1; i<=n; ++i)
    {
        memcpy(g,f,sizeof g);
        for(int wi=w[i],j=wi; j<=m; ++j) (g[j]+=10-g[j-wi])%=10;//g[j]-=g[j-wi]
        for(int j=1; j<=m; ++j) putchar(g[j]+'0');
        putchar('\n');
    }

    return 0;
}