Create A Matrix With Alternating X And 0

Problem Link:

https://www.codingninjas.com/studio/problems/create-a-matrix-with-alternating-x-and-0_981321?leftPanelTabValue=PROBLEM

Hint:

1. Create an array ['X', '0'];

2. Declare a variable 'ind' and initialize it 0.

3. Fill the ans matrix with 'arr[ind]', and after completing on rectangle

   • Do, ind = !ind , it will keep on changing simultaneously.

4. How to iterate,

   • To itertate through 0th row ans n-1th row, only column number will change.

   • Similary to iterate through 0th col and m-1th col, only row number will change.

Code:

#include <bits/stdc++.h> 
vector<vector<char>> constructMatrix(int n, int m)
{
    //    Write your code here.

    vector<vector<char>> ans(n, vector<char>(m,'X'));

    if(n<=2 || m<=2){
        return ans;
    }
    char arr[] = {'X','0'};

    int ind = 0;

    int it1 = 0;
    int mid1 = (n-1)/2;

    int it2 = 0;
    int mid2 = (m-1)/2;

    while(it1<=mid1 && it2<=mid2){

        int row = 0+it1;
        int col = 0+it2;

        for(int i=row;i<n-it1;i++){
            ans[i][col] = arr[ind];
            ans[i][m-1-it2] = arr[ind];
        }

        for(int i=col;i<m-it2;i++){
            ans[row][i] = arr[ind];
            ans[n-1-it1][i] = arr[ind];
        }

        ind = !ind;
        it1++;
        it2++;
    }
    return ans;
}