贪心好题——USACO 2005 October Silver Allowance

http://poj.org/problem?id=3040

注意到这么一句话where each denomination of coin evenly divides the next-larger denomination

想到贪心，排个序，从高往下取

同时加个最小公倍数的优化时间0ms

#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;

int hash1[21];

struct data
{
    int v,b;
}s[29];

int cmp(data a,data b)
{
    return a.v<b.v;
}

int main()
{
    int n,c;
    while(scanf("%d%d",&n,&c)!=EOF)
    {
        int i,j;
        for(i=1;i<=n;i++)
        {
            scanf("%d%d",&s[i].v,&s[i].b);
        }
        sort(&s[1],&s[n+1],cmp);

        int ok=1,add=0,temp,left;
        while(ok)
        {
            left=c;
            for(i=1;i<=n;i++)hash1[i]=0;

            for(i=n;i>=1;i--)
            {
                if(s[i].b==0)continue;

                temp=min(left/s[i].v,s[i].b);
                left=left-temp*s[i].v;
                //s[i].b-=temp;
                hash1[i]=temp;
            }

            if(left!=0)
            for(i=1;i<=n;i++)
            {
                if(left<=0)break;
                if(s[i].b-hash1[i]==0)continue;
                //s[i].b--;
                left-=s[i].v;
                hash1[i]++;
            }
            
            if(left<=0)
            {
                int mmin=9999999;
                for(j=1;j<=n;j++)
                {
                    if(hash1[j]==0)continue;
                    mmin=min(s[j].b/hash1[j],mmin);
                }
                for(j=1;j<=n;j++)
                {
                    if(hash1[j]==0)continue;
                    s[j].b-=mmin*hash1[j];
                }
                add+=mmin;
                //left=c;
            }
            else
                ok=0;
        }

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

    }
}