﻿ C++ : Produce a square matrix with 0s down the main diagonal

# C++ Exercises: Produce a square matrix with 0's down the main diagonal

## C++ For Loop: Exercise-69 with Solution

Write a program in C++ to produce a square matrix with 0's down the main diagonal, 1's in the entries just above and below the main diagonal, 2's above and below that, etc.
0 1 2 3 4
1 0 1 2 3
2 1 0 1 2
3 2 1 0 1
4 3 2 1 0

Visual Presentation:

Sample Solution:-

C++ Code :

``````#include <iostream> // Include input/output stream library
using namespace std; // Use the standard namespace

int main() // Main function where the execution of the program starts
{
int n, i, j, k, m = 0; // Declare integer variables 'n', 'i', 'j', 'k', 'm' and initialize 'm' as 0

cout << "\n\n Print patern........:\n"; // Display message prompting for pattern printing
cout << "-----------------------------------\n"; // Display separator line
cout << " Input number or rows: "; // Prompt user to input the number of rows for the pattern
cin >> n; // Read the number of rows input by the user

for (i = 1; i <= n; i++) { // Outer loop iterating through each row from 1 to 'n'
if (i == 1) { // For the first row,
for (j = 1; j <= i; j++) { // Loop to print 'm' (which is 0) once
cout << m << "  ";
}
for (k = 1; k <= n - i; k++) { // Loop to print numbers from 1 to (n - i)
cout << k << "  ";
}
}
else { // For rows other than the first row,
for (k = i - 1; k >= 1; k--) { // Loop to print numbers in decreasing order from (i - 1) to 1
cout << k << "  ";
}
cout << m << "  "; // Print 'm' (which is 0) once in the middle of the row
for (j = 1; j <= n - i; j++) { // Loop to print numbers from 1 to (n - i)
cout << j << "  ";
}
}
cout << endl; // Move to the next line after printing each row
}
cout << endl; // Add an extra newline at the end
}
``````

Sample Output:

``` Print patern........:
-----------------------------------
Input number or rows: 8
0  1  2  3  4  5  6  7
1  0  1  2  3  4  5  6
2  1  0  1  2  3  4  5
3  2  1  0  1  2  3  4
4  3  2  1  0  1  2  3
5  4  3  2  1  0  1  2
6  5  4  3  2  1  0  1
7  6  5  4  3  2  1  0
```

Flowchart:

C++ Code Editor: