模板：LCS（最长公共子序列）

#include <cstring>

#define max(a,b) ((a) > (b) ? (a) : (b))

int same(char ch1,char ch2)
{
    if(ch1 == ch2) return 1;
    else return 0;
}

int LCS(char *str1,char *str2,int len1,int len2)
{
    int i,j;

    if(len1 < len2) {char *str3 = str1;str1 = str2;str2 = str3;}

    int **dp = new int*[2];
    for(i = 0; i < 2; ++i) dp[i] = new int[len2 + 1];
    memset(dp[0],0,sizeof(int) * (len2 + 1));
    dp[1][0] = 0;

    
    for(i = 1; i <= len1; ++i)
    {
        for(j = 1; j <= len2; ++j)
        {
            dp[i % 2][j] = max(dp[(i - 1) % 2][j],max(dp[i % 2][j - 1],dp[(i - 1) % 2][j - 1] + same(str1[i - 1],str2[j - 1])));
            //cout<<"dp[" << i << "][" << j << "]=" << dp[i % 2][j] << endl;
        }
    }
    int max = dp[len1 % 2][len2];

    for(i = 0; i < 2; ++i) delete [] dp[i];
    delete [] dp;

    return max;
}