HDU2126 二维背包

HDU2126

对背包还是不太熟练啊…刚开始看背包，于是做到这些题目满脑子都是放入体积为XXX的最大价值为XXX，在这道题上就想了很久，后来再次看了一看背包九讲又多理解了一点，这道题可以用三维数组来表示dp[i][j][k]为前i个物品选j个总价钱为k的方案数，状态转移方程为dp[i][j][k] =dp[i-1][j][k] + dp[i-1][j-1][k-c[i]],再用空间优化见代码，另外注意初始化dp[0][0] = 1就好了

Description

When the winter holiday comes, a lot of people will have a trip. Generally, there are a lot of souvenirs to sell, and sometimes the travelers will buy some ones with pleasure. Not only can they give the souvenirs to their friends and families as gifts, but also can the souvenirs leave them good recollections. All in all, the prices of souvenirs are not very dear, and the souvenirs are also very lovable and interesting. But the money the people have is under the control. They can’t buy a lot, but only a few. So after they admire all the souvenirs, they decide to buy some ones, and they have many combinations to select, but there are no two ones with the same kind in any combination. Now there is a blank written by the names and prices of the souvenirs, as a top coder all around the world, you should calculate how many selections you have, and any selection owns the most kinds of different souvenirs. For instance:

And you have only 7 RMB, this time you can select any combination with 3 kinds of souvenirs at most, so the selections of 3 kinds of souvenirs are ABC (6), ABD (7). But if you have 8 RMB, the selections with the most kinds of souvenirs are ABC (6), ABD (7), ACD (8), and if you have 10 RMB, there is only one selection with the most kinds of souvenirs to you: ABCD (10).

Input

For the first line, there is a T means the number cases, then T cases follow.
In each case, in the first line there are two integer n and m, n is the number of the souvenirs and m is the money you have. The second line contains n integers; each integer describes a kind of souvenir.
All the numbers and results are in the range of 32-signed integer, and 0<=m<=500, 0

Output

If you can buy some souvenirs, you should print the result with the same formation as “You have S selection(s) to buy with K kind(s) of souvenirs”, where the K means the most kinds of souvenirs you can buy, and S means the numbers of the combinations you can buy with the K kinds of souvenirs combination. But sometimes you can buy nothing, so you must print the result “Sorry, you can’t buy anything.”

Sample Input

2
4 7
1 2 3 4

4 0
1 2 3 4

Sample Output

You have 2 selection(s) to buy with 3 kind(s) of souvenirs.
Sorry, you can’t buy anything.

代码

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<algorithm>using namespace std;int dp[31][501];int main(){   int t;   while (scanf("%d",&t) != EOF)   {           for (int start = 0;start < t;start++)           {                int n,m;                int c[31];                memset(c,0,sizeof(c));                memset(dp,0,sizeof(dp));                dp[0][0] = 1;//                scanf("%d%d",&n,&m);                for (int i = 0;i<n;i++)                {                    scanf("%d",&c[i]);                }                for (int i = 0;i<n;i++)                   for (int j = n;j>=1;j--)                     for (int k = m;k>=c[i];k--)                        dp[j][k] = dp[j][k] +dp[j-1][k-c[i]];                int ans = 0;                for (int j = n;j>=1;j--)                {                        for (int k = m;k>=0;k--)                          ans+=dp[j][k];                          if (ans)                          {                            printf("You have %d selection(s) to buy with %d kind(s) of souvenirs.\n",ans,j);                            break;                          }                }                if (!ans)                  printf("Sorry, you can't buy anything.\n");           }   }}