学步园

zoj2156

用一个结构体pre数组来记录前一步的信息

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

int C,n[30],v[5]={
	0,1,5,10,25
};
int dp[15000];
struct PRE
{
	int ID,NUM,P;
} pre[15000];

int main()
{
	int i,j,k,x;
	while(1)
	{
		scanf("%d%d%d%d%d",&C,&n[1],&n[2],&n[3],&n[4]);
		if(!(C|n[1]|n[2]|n[3]|n[4]))	break;
		
		for(i=0;i<=C;i++){
			dp[i]=-1;
			pre[i].ID=i;
			pre[i].NUM=pre[i].P=0;
		}dp[0]=0;
		
		for(i=1;i<=4;i++)
		{
			x=1;
			while(n[i]>0){
				if(x>n[i])	x=n[i];n[i]-=x;
				
				for(j=C;j>=x*v[i];j--)	if(dp[j-x*v[i]]>=0&&dp[j]<dp[j-x*v[i]]+x){
					dp[j]=dp[j-x*v[i]]+x;
					pre[j].ID=j-x*v[i];
					pre[j].NUM=x;
					pre[j].P=v[i];
				}
				x*=2;
			}
		}
	//	for(i=1;i<=C;i++)	printf("%d ",pre[i].ID);printf("\n");//while(1);
	//	for(i=1;i<=C;i++)	printf("%d ",dp[i]);printf("\n");
		if(dp[C]>0){
			for(memset(n,0,sizeof(n)),x=C;x!=0;x=pre[x].ID)	n[pre[x].P]+=pre[x].NUM;
			printf("Throw in %d cents, %d nickels, %d dimes, and %d quarters.\n",n[1],n[5],n[10],n[25]);
		}	
		else	printf("Charlie cannot buy coffee.\n");
	}
	
	
	return 0;
}