poj1159 dp最长公共子串

 1 //Accepted    204 KB    891 ms
 2 //dp最长公共子串
 3 //dp[i][j]=max(dp[i-1][j],dp[i][j-1])
 4 //dp[i][j]=max(dp[i][j],dp[i-1][j-1]+1) (s1[i]==s2[j])
 5 #include <cstdio>
 6 #include <cstring>
 7 #include <iostream>
 8 using namespace std;
 9 const int imax_n = 5002;
10 int dp[2][imax_n];
11 char s1[imax_n];
12 char s2[imax_n];
13 int n;
14 int max(int a,int b)
15 {
16     return a>b?a:b;
17 }
18 void Dp()
19 {
20     memset(dp,0,sizeof(dp));
21     for (int i=1;i<=n;i++)
22     {
23         for (int j=1;j<=n;j++)
24         {
25             dp[i%2][j]=max(dp[(i-1)%2][j],dp[i%2][j-1]);
26             if (s1[i-1]==s2[j-1])
27             dp[i%2][j]=max(dp[i%2][j],dp[(i-1)%2][j-1]+1);
28         }
29     }
30     printf("%d\n",n-dp[n%2][n]);
31 }
32 int main()
33 {
34     while (scanf("%d",&n)!=EOF)
35     {
36         scanf("%s",s1);
37         for (int i=0;i<n;i++)
38         s2[i]=s1[n-1-i];
39         s2[n]=‘\0‘;
40         Dp();
41     }
42     return 0;
43 }