poj 3211 Washing Clothes

 http://poj.org/problem?id=3211

神奇01背包。

只是有多组0-1背包，即每种颜色进行一次背包选择。
> 选择的方式是先截取每种颜色总时间的一半，也就是说，至少要消耗一半的时间。
> 然后用做 f[一半的时间] 数组最大值，背包之后，用总的时间减去得到的f[一半的时间]的最大值的差值，是消耗的最少时间。

数组一定要开得很大。

Washing Clothes

Time Limit: 1000MS		Memory Limit: 131072K
Total Submissions: 8478		Accepted: 2636

Description

Dearboy was so busy recently that now he has piles of clothes to wash. Luckily, he has a beautiful and hard-working girlfriend to help him. The clothes are in varieties of colors but each piece of them can be seen as of only one color. In order to prevent the clothes from getting dyed in mixed colors, Dearboy and his girlfriend have to finish washing all clothes of one color before going on to those of another color.

From experience Dearboy knows how long each piece of clothes takes one person to wash. Each piece will be washed by either Dearboy or his girlfriend but not both of them. The couple can wash two pieces simultaneously. What is the shortest possible time they need to finish the job?

Input

The input contains several test cases. Each test case begins with a line of two positive integers M and N (M < 10, N < 100), which are the numbers of colors and of clothes. The next line contains M strings which are not longer than 10 characters and do not contain spaces, which the names of the colors. Then follow N lines describing the clothes. Each of these lines contains the time to wash some piece of the clothes (less than 1,000) and its color. Two zeroes follow the last test case.

Output

For each test case output on a separate line the time the couple needs for washing.

Sample Input

3 4
red blue yellow
2 red
3 blue
4 blue
6 red
0 0

Sample Output

10

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
int v[200][200],num[100010];
int dp[100010],sum[100010];
char str[20][20],str1[20];
using namespace std;
int main()
{
    int m,n,i,r,j,q,t;
    int k,ans;
    while(~scanf("%d%d",&m,&n))
     {
        if(n==0||m==0)
           break;
       for(i=0;i<m;i++)
          scanf("%s",str[i]);
          memset(num,0,sizeof(num));
        for(i=0;i<n;i++)
        {
            scanf("%d",&t);
            scanf("%s",str1);
           for(j=0;j<m;j++)
           {
              if(strcmp(str1,str[j])==0)
                  {
                      v[j][num[j]]=t;
                       num[j]++;
                       break;
                  }
            }
        }
      for(i=0;i<m;i++)
      {
          sum[i]=0;
          for(j=0;j<num[i];j++)
         {
             sum[i]+=v[i][j];
         }
      }
         ans=0;
     for(i=0;i<m;i++)
      {
          memset(dp,0,sizeof(dp));
          for(j=0;j<num[i];j++)
           for(k=sum[i]/2;k>=v[i][j];k--)
              {
               dp[k]=max(dp[k],dp[k-v[i][j]]+v[i][j]);//01背包。
              }
          ans+=sum[i]-dp[sum[i]/2];
      }
      printf("%d\n",ans);
     }
    return 0;
}