HDU2602 Bone Collector(01背包)

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题目:

Bone Collector

**Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 53983    Accepted Submission(s): 22616
**
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Problem Description

Many years ago , in Teddy’s hometown there was a man who was called “Bone Collector”. This man like to collect varies of bones , such as dog’s , cow’s , also he went to the grave …
The bone collector had a big bag with a volume of V ,and along his trip of collecting there are a lot of bones , obviously , different bone has different value and different volume, now given the each bone’s value along his trip , can you calculate out the maximum of the total value the bone collector can get ?\

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Input

The first line contain a integer T , the number of cases.
Followed by T cases , each case three lines , the first line contain two integer N , V, (N <= 1000 , V <= 1000 )representing the number of bones and the volume of his bag. And the second line contain N integers representing the value of each bone. The third line contain N integers representing the volume of each bone.

 

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Output

One integer per line representing the maximum of the total value (this number will be less than 2 31).

 

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Sample Input

  
  

   
   1
5 10
1 2 3 4 5
5 4 3 2 1
  
  

 

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Sample Output

  
  

   
   14
  
  

 

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Author

Teddy

 

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Source

HDU 1st “Vegetable-Birds Cup” Programming Open Contest

 

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题意:

意思是一个人有收集骨头的习惯,现在他有一个背包,面前有不同的骨头种类和各自对应的价值,求这个背包能装的最大价值,这些东西不可分割,所以不能用贪心,也就是01背包问题

代码一(一维):

#include <stdio.h>
#include <string.h>
#include <algorithm>
#define mem(a,b) memset(a,b,sizeof(a));
using namespace std;
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n,v;//个数 和 容量
        scanf("%d %d",&n,&v);
        int a[1010],b[1010];
        for(int i=0; i<n; i++)
            scanf("%d",&a[i]);//每一个的价值
        for(int i=0; i<n; i++)
            scanf("%d",&b[i]);//每一个的体积
        int dp[1010];//定义状态
        mem(dp,0);
        for(int i=0; i<n; i++)
        {
            for(int j=v; j>=b[i]; j--)//逆序
                dp[j]=max(dp[j],dp[j-b[i]]+a[i]);
        }
        printf("%d\n",dp[v]);
    }
    return 0;
}
//dp[i][v]是由dp[i-1][v]和dp[i-1][v-c[i]]两个子问题递推而来,能否保证在推dp[i][v]时(也即在第i次主循环中推dp[v]时)能够得到dp[i-1][v]和dp[i-1][v-c[i]]的值呢?事实上,这要求在每次主循环中我们以v=V..0的顺序推dp[v],这样才能保证推dp[v]时dp[v-c[i]]保存的是状态dp[i-1][v-c[i]]的值。伪代码如下:
//        for i=1..N
//              for v=V..0
//                        dp[v]=max{dp[v],dp[v-c[i]]+w[i]};
//注意:这种解法只能由V--0,不能反过来,如果反过来就会造成物品重复放置!

代码二(二维):

#include <stdio.h>
#include <string.h>
#include <algorithm>
#define mem(a,b) memset(a,b,sizeof(a));
using namespace std;
int dp[1000][1000];//定义状态
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n,v;//个数 和 容量
        scanf("%d %d",&n,&v);
        int a[1010],b[1010];
        for(int i=1; i<=n; i++)
            scanf("%d",&a[i]);//每一个的价值
        for(int i=1; i<=n; i++)
            scanf("%d",&b[i]);//每一个的体积
        mem(dp,0);
        for(int i=1; i<=n; i++)//遍历个数
        {
            for(int j=0; j<=v; j++)//遍历背包容量
            {
                if(b[i]<=j)//可以放进去
                    dp[i][j]=max(dp[i-1][j],dp[i-1][j-b[i]]+a[i]);//第i个物品放入后,那么前i-1个物品可能会放入也可能因为剩余空间不够无法放入
                else//不能放进去
                    dp[i][j]=dp[i-1][j];
            }
        }
        printf("%d\n",dp[n][v]);
    }
    return 0;
}

ps:

01背包问题,这种背包特点是:每种物品仅有一件,可以选择放或不放。
用子问题定义状态:即dp[i][v]表示前i件物品恰放入一个容量为v的背包可以获得的最大价值。
则其状态转移方程便是:
dp[i][v]=max{dp[i-1][v],dp[i-1][v-cost[i]]+value[i]}

另NYOJ289 苹果和这道题很相似

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