poj 1159 (DP LCS)

滚动数组 + LCS

 1 // File Name: 1159.cpp

 2 // Author: Missa_Chen

 3 // Created Time: 2013年07月08日 星期一 10时07分13秒

 4 

 5 #include <iostream>

 6 #include <string>

 7 #include <algorithm>

 8 #include <cstdio>

 9 #include <cstring>

10 #include <cmath>

11 #include <queue>

12 #include <map>

13 #include <stack>

14 #include <set>

15 #include <cstdlib>

16 #include <vector>

17 #include <time.h>

18 

19 using namespace std;

20 

21 const int maxn = 5e3 + 5;

22 int n;

23 char buf[maxn];

24 int LCS(string s1, string s2)

25 {

26     int dp[2][maxn] = {0};

27     int e = 0;

28     for (int i = 1; i <= n; ++i)

29     {

30         e = 1 - e;

31         for (int j = 1; j <= n; ++j)

32             if (s1[i - 1] == s2[j - 1])

33                 dp[e][j] = dp[1 - e][j - 1] + 1;

34             else dp[e][j] = max (dp[1 - e][j], dp[e][j - 1]);

35     }

36     return dp[e][n];

37 }

38 int main()

39 {

40     while (~scanf("%d",&n))

41     {

42         scanf("%s", buf);

43         string s, rev;

44         s = rev = buf;

45         reverse(rev.begin(), rev.end());

46         printf("%d\n", n - LCS(s, rev));

47     }

48     return 0;

49 }