longest common subsequence by dp

#include<iostream>
#include<cstring>
#include<math.h>
using namespace std;

int LCS(char str1[],char str2[],int l1,int l2){
  if(l1==0 ||l2==0)
    return 0;
  int arr[l1+1][l2+1];
  for(int i=0;i<=l1;i++){
    for(int j=0;j<=l2;j++){
      if(i==0 || j==0)
        arr[i][j]=0;
      else{
          if(str1[i-1]==str2[j-1])
            arr[i][j]=1+arr[i-1][j-1];
          else
            arr[i][j]=max(arr[i][j-1],arr[i-1][j]);
          }
      }
    }
    return arr[l1][l2];
  }

int main(){
  char X[] = "AGGTAB";
  char Y[] = "GXTXAYB";
  int m = strlen(X);
  int n = strlen(Y);
  cout<<"Length of LCS is "<<LCS( X, Y, m, n ) ;
  return 0;
  }