USACO3.15stamps（dp）

对dp很无奈。。枚举所有可能达到的值 dp[i]表示到达i值所用最少的邮票 

 1 /*
 2     ID: shangca2
 3     LANG: C++
 4     TASK: stamps
 5 */
 6 #include <iostream>
 7 #include<cstdio>
 8 #include<cstring>
 9 #include<stdlib.h>
10 #include<algorithm>
11 using namespace std;
12 int p[55],dp[2000010];
13 bool o[2000010];
14 int main()
15 {
16     freopen("stamps.in","r",stdin);
17     freopen("stamps.out","w",stdout);
18     int i,j,k,n;
19     cin>>n>>k;
20     for(i = 1 ; i <= k ; i++)
21     {
22         cin>>p[i];
23         o[p[i]] = 1;
24         dp[p[i]] = 1;
25     }
26     for(i = 1 ; ; i++)
27     {
28         if(o[i]&&dp[i]<n)
29         {
30             for(j = 1 ; j <= k ;j++)
31             {
32                 o[i+p[j]] = 1;
33                 if(dp[i+p[j]]==0)
34                 dp[i+p[j]] = dp[i]+1;
35                 else
36                 dp[i+p[j]] = min(dp[i]+1,dp[i+p[j]]);
37             }
38         }
39         else if(!o[i])
40         {
41             printf("%d\n",i-1);
42             break;
43         }
44     }
45     return 0;
46 }
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posted @ 2013-05-28 19:32  _雨  阅读(202)  评论(0)  编辑  收藏  举报