HDU 1709 The Balance

题解：因为天平两边都可以放砝码，所以需要再建一个负的砝码值，然后用母函数即可……

#include <cstdio>

#include <iostream>  

using namespace std;   

int c1[10005],c2[10005],n,sum,res,weight[105];  

int main(){  

    while(scanf("%d",&n)!=EOF){  

        res=sum=0;  

        for(int i=0;i<n;i++){  

            scanf("%d",&weight[i]);   

            sum+=weight[i];  

            weight[n+i]=-weight[i];  

        }  

        memset(c1,0,sizeof(c1)); memset(c2,0,sizeof(c2));  

        for(int i=0;i<=weight[0];i+=weight[0])c1[i]=1;  

        for(int i=1;i<2*n;i++){  

            for(int j=0;j<10005;j++){  

                if(i<=n-1){  

                    for(int k=0;k<=weight[i];k+=weight[i])c2[j+k]+=c1[j];  

                }else{  

                    for(int k=weight[i];k<=0;k+=-weight[i]){  

                        if(j+k>=0)c2[j+k]+=c1[j];  

                    }  

                }  

            }for(int j=0;j<10005;j++)c1[j]=c2[j],c2[j]=0;  

        }for(int i=0;i<=sum;i++)if(c1[i]==0)res++;  

        bool flag=false;  

        printf("%d\n",res);  

        if(res!=0){  

            for(int i=0;i<=sum;i++){  

                if(c1[i]==0&&flag==false){  

                    printf("%d",i);  

                    flag=true;  

                }  

                else if(c1[i]==0&&flag)printf(" %d",i);  

            }printf("\n");  

        }  

    }return 0;  

}