母函数求解:
需要注意一点,有个结论,但我还查不到这个结论哪里来的。。。
如果n>=8,可将n改写为12(n为偶数),或者11(为奇数)。
#include<cstdio>
#include<cstring>
using namespace std;
int a[7];
const int maxn=3e7;
int x[maxn];
int y[maxn];
int main(){
int T=1;
while(1){
int ans=0;
for(int i=1;i<=6;i++){
scanf("%d",&a[i]);
if(a[i]>8&&a[i]%2) a[i]=11;
else if(a[i]>8) a[i]=12;
ans+=a[i]*i;
}
if(!ans) break;
printf("Collection #%d:\n",T++);
if(ans%2){
printf("Can't be divided.\n\n");
}else{
for(int i=0;i<=ans/2;i++){
x[i]=y[i]=0;
}
x[0]=1;
int t=ans/2;
for(int i=1;i<=6;i++){
for(int j=0;j<=t;j++){
for(int k=0;k<=a[i]&&(j+k*i)<=t;k++){
y[j+k*i]+=x[j];
}
}
for(int j=0;j<=t;j++){
x[j]=y[j];
y[j]=0;
}
}
if(x[t]){
printf("Can be divided.\n\n");
}else{
printf("Can't be divided.\n\n");
}
}
}
}
/*
3
2 7
7 2
5 5
*/
也可以转化为背包问题:
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int a[7];
const int maxn=3e7;
int dp[maxn];
int v[maxn];
int main(){
int T=1;
while(1){
int sum=0;
for(int i=1;i<=6;i++){
scanf("%d",&a[i]);
sum+=a[i]*i;
}
if(!sum) break;
printf("Collection #%d:\n",T++);
if(sum%2){
printf("Can't be divided.\n\n");
}else{
int f=sum/2;
int len=0;
for(int i=1;i<=6;i++){
int num=a[i];
int c=1;
while(num-c>0){
num-=c;
v[++len]=c*i;
c<<=1;
}
if(num)
v[++len]=num*i;
}
for(int i=0;i<=f;i++){
dp[i]=0;
}
for(int i=1;i<=len;i++){
for(int j=f;j>=v[i];j--){
dp[j]=max(dp[j],dp[j-v[i]]+v[i]);
}
}
if(dp[f]==f){
printf("Can be divided.\n\n");
}else{
printf("Can't be divided.\n\n");
}
}
}
return 0;
}
/*
3
2 7
7 2
5 5
*/