01背包 URAL 1073 Square Country

 1 /*
 2     题意：问n最少能是几个数的平方和
 3     01背包：j*j的土地买不买的问题
 4     详细解释：http://www.cnblogs.com/vongang/archive/2011/10/07/2200721.html
 5 */
 6 #include <cstdio>
 7 #include <algorithm>
 8 #include <cmath>
 9 #include <cstring>
10 using namespace std;
11 
12 const int MAXN = 6e4 + 10;
13 const int INF = 0x3f3f3f3f;
14 int dp[MAXN];
15 
16 int main(void)        //URAL 1073 Square Country
17 {
18     //freopen ("I.in", "r", stdin);
19 
20     int n;
21     while (scanf ("%d", &n) == 1)
22     {
23         memset (dp, 0, sizeof (dp));
24         for (int i=1; i<=n; ++i)
25         {
26             dp[i] = dp[i-1] + 1;
27             for (int j=2; j<=sqrt (n*1.0); ++j)
28             {
29                 if (i >= j * j)    dp[i] = min (dp[i], dp[i-j*j] + 1);
30                 else    break;
31             }
32         }
33 
34         printf ("%d\n", dp[n]);
35     }
36 
37 
38     return 0;
39 }