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LCS (how can i improve this code)

I created this code using dynamic programming approach but the code is not display the result. the code is as follows:

#include <iostream>
using namespace std;

void LCS(int input1[], int input2[], int n, int m) {
    int L[n + 1][m + 1];  /*This matrix stores the length of common subsequences*/
    for (int i = 0; i <= n; i++) {
        for (int j = 0; j <= m; j++) {
            if (i == 0 || j == 0)
                L[i][j] = 0;
            else if (input1[i - 1] == input2[j - 1]) 
                L[i][j] = 1 + L[i - 1][j - 1]; 
            else
                L[i][j] = max(L[i - 1][j], L[i][j - 1]);
        }
    }
    int index = L[n][m];
    int lcs[index];
    int i = n, j = m;
    while (i > 0 && j > 0) {
        if (input1[i - 1] == input2[j - 1]) {
            lcs[index - 1] = input1[i - 1];
            i--;
            j--;
            index--;
        } else if (L[i - 1][j] > L[i][j - 1])
            i--;
        else
            j--;

    }
    for (int i = 0; i < index; i++){
        cout << lcs[i];
    }

}
int main() {
    int n, m;
    cin >> n >> m;
    int input1[n], input2[m]; /*two arrays from which longest subsequnce is to be found*/
    for (int i = 0; i < n; i++)
        cin >> input1[i];
    for (int i = 0; i < m; i++)
        cin >> input2[i];
    LCS(input1, input2, n, m);
    return 0;
}

The code terminates without showing any result!

I even switched to a different IDE but its the same. What is wrong with this? Please help.

asked Sep 26, 2016 by nrb

2 Answers

In c++, Variable length arrays are not legal such as input1[n] intput2[m];

 if you want to use variable length array  then you will have to allocate memory dynamically for an arrays.for example

double* input[n]=new double[n]; Don't forget to delete when you're done .

 

or you can use standard container

 
std::vector<double> intput(n); by including <vector.h> library.

 
answered Sep 28, 2016 by 4nkush
for (int i = 0; i < index; i++){
        cout << lcs[i];
In last loop of your function index value reached at 0 and 
you are using i < index this will i < 0 so 
there will nothing in output. 
Just relace index = L[n][m] you will get answer.

// corrected loop will be

index = L[n][m];

 

for ( int i = 0 ; i < index ; i++)

cout << lcs[i];

Hope it will help you if not then let me know.

answered Sep 29, 2016 by Hariom Singh Bais
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