poj1159(动态规划或者lcs求最长字串)

 http://acm.hrbust.edu.cn/vj/index.php?c=problem-problem&id=20480

LCS求最长公共子串

#include<stdio.h>
#include<iostream>
#include<map>
#include<string.h>
#include<vector>
using namespace std;
short a[5005][5005];
char s1[5005];
char s2[5005];
int LCS(const char *s1, const char *s2)
{
    // s1:0...m, s2:0...n
    int m = strlen(s1), n = strlen(s2);
    int i, j;
    a[0][0] = 0;
    for( i=1; i <= m; ++i )
        a[i][0] = 0;
    for( i=1; i <= n; ++i )
        a[0][i] = 0;
    for( i=1; i <= m; ++i )
        for( j=1; j <= n; ++j )
        {
            if(s1[i-1]==s2[j-1])
                a[i][j] = a[i-1][j-1]+1;
            else if(a[i-1][j]>a[i][j-1])
                a[i][j]= a[i-1][j];
            else
                a[i][j] = a[i][j-1];
        }
    return a[m][n];
}

int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        memset(s1,0,sizeof(s1));
        memset(s2,0,sizeof(s2));
        for(int i=0; i<n; i++)
        {
            cin>>s1[i];
        }
        for(int i=0; i<n; i++)
        {
            s2[i]=s1[n-i-1];
        }
        //cout<<s1<<" "<<s2<<endl;
        cout<<n-LCS(s1,s2)<<endl;
    }
}

动态规划 注意short类型，不然会超内存；

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<math.h>
using namespace std;
short dp[5001][5001];
int main()
{
    int k;
    char a[5001],b[5001];
    while(~scanf("%d",&k))
    {
        scanf("%s",a);
        int p=0;
        for(int i=k-1; i>=0; i--)
        {
            b[p]=a[i];
            p++;
        }
        //for(int i=0; i<k; i++)
           // printf("%c%c",b[i],(i==(k-1))?'\n':' ');
        memset(dp,0,sizeof(0));
        for(int i=1; i<=k; i++)
            for(int j=1; j<=k; j++)
            {
                if(a[i]==b[j]) dp[i][j]=dp[i-1][j-1]+1;
                else
                    dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
            }
           // printf("%d\n",dp[k][k]);
        printf("%d\n",k-dp[k][k]);

    }
}