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  1. Prepare
  2. C++
  3. Introduction
  4. Variable Sized Arrays
  5. Discussions

Variable Sized Arrays

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  • fahad_khan44604
     + 0 comments

    The following include two solutions

    1. Using Vectors
    int main() {
    int rows, q;
    cin >> rows >> q;
    
    vector<vector<int>> matrix(rows);
    for(int i=0; i<rows; i++) {
       int cols;
       cin >> cols;
       matrix[i].resize(cols);
       
       for(int j=0; j<cols; j++) cin >> matrix[i][j];
    }
    
    // for query part
    for(int i=0; i<q; i++) {
        int row, col;
        cin >> row >> col;
        cout << matrix[row][col] << endl;
    }
    return 0;
}
    1. Using normal Arrays
    int main() {
    int rows, q;
    cin >> rows >> q;
    
    int ** matrix = new int*[rows];
    
    // taking inputs
    for(int i=0; i<rows; i++) {
       int cols;
       cin >> cols;
       matrix[i] = new int[cols];
       
       for(int j=0; j<cols; j++) cin >> matrix[i][j];
    }
    
    // for query part
    for(int i=0; i<q; i++) {
        int row, col;
        cin >> row >> col;
        cout << matrix[row][col] << endl;
    }
    
    // delete dynamically allocated memory
    for(int i=0; i<rows; i++) {
        delete[] matrix[i];
    }
    delete[] matrix;
    return 0;
}

    The logic is same TC -> O(n * m) where n is rows and m is columns

  • Shamanand1y2
     + 0 comments
    #include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main(){
        int a,b,x;
        cin>>a>>b;
        int* arr[a];
        int c[b][2],d[a];
        vector<int> v;
        for(int i=0;i<a;i++){
                int k;
                cin>>k;
                for(int j=0;j<k;j++){
                        cin>>x;
                        v.push_back(x);
                }
                d[i]=k;
                }
        for(int k=0;k<b;k++){
                cin>>(c[k][0])>>(c[k][1]);
        }
        int* p = &v[0];
        for(int i=0;i<a;i++){
            arr[i]=p;
            p += d[i]; 
        }
        for(int i=0;i<b;i++){
            cout<<*(arr[c[i][0]] + c[i][1])<<endl;
        }

                            }

  • saumya_vhm
     + 0 comments

    include

    include

    include

    include

    include

    using namespace std;

    int main() { int n , q ; cin >> n >> q ; vector> arr(n);

    for(int i = 0 ; i < n ; i++){
    int k ;
    cin >> k ;
    arr[i].resize(k); 
    for(int j = 0 ; j<k ; j++){
        cin >>arr[i][j];
    }
}

for (int i = 0 ; i < q ; i++){
    int x,y;
    cin >>x>> y ;
    cout <<arr[x][y] << endl;

}


return 0;

    }

  • yashdeora98294
     + 0 comments

    Here is Variable sized arrays solution in c++ - https://programmingoneonone.com/hackerrank-variable-sized-arrays-solution-in-cpp.html

  • mogaro
     + 1 comment

    I didn't really did a proper research about how to define the size of the vectors so I ended by making this code

    int main() {
    vector<vector<int>> matrix, querys;
    int n, q, lenght, x, y;
    
    cin >> n >> q;
    
    for(int i=0; i < n; i++){
        cin >> lenght;
        matrix.push_back(vector<int> ());
        
        for (int j=0; j < lenght; j++) {
            cin >> x;
            matrix[i].push_back(x);
        }
    }
    
    for (int i=0; i < q; i++) {
        cin >> x >> y;
        querys.push_back(vector<int> ());
        querys[i].push_back(x);
        querys[i].push_back(y);
    }
    
    for (int i=0; i < q; i++) {
        cout << matrix[querys[i][0]][querys[i][1]] << endl;
    }
     
    return 0;
}