HDU 1513 Palindrome

 1 //#define LOCAL
 2 #include <iostream>
 3 #include <cstring>
 4 #include <algorithm>
 5 #include <cstring>
 6 using namespace std;
 7 
 8 const int maxn = 5000 + 5;
 9 char s1[maxn], s2[maxn];
10 int dp[2][maxn];
11 
12 void Reverse(char str[], int len)
13 {
14     int i, t;
15     for(i = 0; i < len/2; ++i)
16     {
17         t = str[i];
18         str[i] = str[len - 1 - i];
19         str[len - 1 - i] = t;
20     }
21 }
22 
23 int main(void)
24 {
25     #ifdef LOCAL
26         freopen("1513in.txt", "r", stdin);
27     #endif
28     int len;
29     while(scanf("%d", &len) == 1)
30     {
31         scanf("%s", s1);
32         memcpy(s2, s1, sizeof(s1));
33         Reverse(s2, len);
34         int i, j;
35         memset(dp, 0, sizeof(dp));
36         int cur = 1,ans;
37         for(i = 1; i <= len; ++i)
38         {
39             for(j = 1; j <= len; ++j)
40             {
41                 if(s1[i-1] == s2[j-1])
42                     dp[cur][j] = dp[1-cur][j-1] + 1;
43                 else
44                     dp[cur][j] = max(dp[1-cur][j], dp[cur][j-1]);
45             }
46             cur = 1 - cur;
47         }
48         ans = len - dp[len&1][len];
49         printf("%d\n", ans);
50     }
51     return 0;
52 }