Problem 15.5 from Cormen's book: longest palindromic sequence

App.cpp

/**
For example if the input is "charachter" the output shout be "carac"
*/
#include <iostream>
#include <string>
class CostArray{
    int *cost;
    int width;
    public:
        CostArray(int m, int n):width(n){
            cost = new int[m*n] ;
         }
        int get(int i, int j) const{
            if (i<0 || j<0) return 0;
            else return cost[i*width+j];
        }
        void set(int i, int j, int val){
             cost[i*width+j] = val;
        }

};
using std::string;
CostArray ComputeArray(string const& X, string const& Y){
    CostArray cost(X.length(),Y.length());
    for(int i=0; i<X.length(); ++i)
    for(int j=0; j<Y.length(); ++j){
            if(X[i] == Y[j]){
                cost.set(i,j,cost.get(i-1,j-1)+1);
            }else {

            int x = cost.get(i-1,j);
            int y = cost.get(i,j-1);
            cost.set(i,j,std::max(x,y));
            }
    }
    return cost;
}
void PrintSequence(CostArray const& cost, string const& X, string const& Y, int i, int j){
    if(i<0 || j<0) return;
    else if(X[i]==Y[j]){
        PrintSequence(cost,X,Y,i-1,j-1);
        std::cout << X[i];
    }else if( cost.get(i-1,j)<cost.get(i,j-1)){
        PrintSequence(cost, X,Y,i,j-1);
    } else {
        PrintSequence(cost,X,Y,i-1,j);
    }
}

int test(int argc, char* argv[]){
    if (argc<3){
        std::cout << "requires two string arguments" << "\n";
    }
    string X=argv[1];
    string Y=argv[2];
    CostArray cost = ComputeArray(X,Y);
    PrintSequence(cost,X,Y,X.length()-1,Y.length()-1);
    return 0;
}
int main(int argc, char* argv[]){
    if (argc<2){
        std::cout << "requires one string argument" << "\n";
    }
    string X=argv[1];
    string Y(X.rbegin(),X.rend());
    std::cout << X << " " << Y << "\n";
    CostArray cost = ComputeArray(X,Y);
    PrintSequence(cost,X,Y,X.length()-1,Y.length()-1);
    std::cout<<std::endl;
    return 0;
}