poj 1159 (DP LCS)

滚动数组 + LCS

// File Name: 1159.cpp
// Author: Missa_Chen
// Created Time: 2013年07月08日 星期一 10时07分13秒

#include <iostream>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <queue>
#include <map>
#include <stack>
#include <set>
#include <cstdlib>
#include <vector>
#include <time.h>

using namespace std;

const int maxn = 5e3 + 5;
int n;
char buf[maxn];
int LCS(string s1, string s2)
{
    int dp[2][maxn] = {0};
    int e = 0;
    for (int i = 1; i <= n; ++i)
    {
        e = 1 - e;
        for (int j = 1; j <= n; ++j)
            if (s1[i - 1] == s2[j - 1])
                dp[e][j] = dp[1 - e][j - 1] + 1;
            else dp[e][j] = max (dp[1 - e][j], dp[e][j - 1]);
    }
    return dp[e][n];
}
int main()
{
    while (~scanf("%d",&n))
    {
        scanf("%s", buf);
        string s, rev;
        s = rev = buf;
        reverse(rev.begin(), rev.end());
        printf("%d
", n - LCS(s, rev));
    }
    return 0;
}