HDU 1159 Common Subsequence(LCS)

#include <iostream>
#include <cstring>

using namespace std;

const int MAX_N = 1000 + 100;
char a[MAX_N],b[MAX_N];
int dp[MAX_N][MAX_N];

int main()
{
    while(cin >> a >> b)
    {
        int len1 = strlen(a);
        int len2 = strlen(b);
        for(int i = 0;i <= len1;i++)
            dp[i][0] = 0;
        for(int j = 0;j <= len2;j++)
            dp[0][j] = 0;
        for(int i = 1;i <= len1;i++)
        {
            for(int j = 1;j <= len2;j++)
            {
                if(a[i - 1] == b[j - 1])
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                else
                    dp[i][j] = max(dp[i - 1][j],dp[i][j - 1]);
            }
        }
        cout << dp[len1][len2] << endl;
    }
    return 0;
}