Diamond Pattern in C++

Diamond in C++: full pyramid plus inverted from rows-1. Input 5 is 9 lines, not 5.

IntermediateAdvanced Pattern ProgramsExample 3 of 6

diamond-pattern.cpp

1#include <iostream>
2using namespace std;
3
4int main() {
5    int rows;
6    
7    cout << "Enter number of rows (half): ";
8    cin >> rows;
9    
10    // Upper part of diamond
11    for (int i = 1; i <= rows; i++) {
12        for (int j = 1; j <= rows - i; j++) {
13            cout << " ";
14        }
15        for (int j = 1; j <= 2 * i - 1; j++) {
16            cout << "*";
17        }
18        cout << endl;
19    }
20    
21    // Lower part of diamond
22    for (int i = rows - 1; i >= 1; i--) {
23        for (int j = 1; j <= rows - i; j++) {
24            cout << " ";
25        }
26        for (int j = 1; j <= 2 * i - 1; j++) {
27            cout << "*";
28        }
29        cout << endl;
30    }
31    
32    return 0;
33}

Output

Enter number of rows (half): 5
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

What's going on

A diamond is a full pyramid glued to an inverted pyramid, without printing the fat middle twice.

cin >> rows; is the half-height. Sample 5 → 9 lines total (5 up, 4 down).

Upper half — identical to Full Pyramid:

spaces rows - i, stars 2 * i - 1. i = 1..rows → 1, 3, 5, 7, 9 stars.

Lower half:

for (int i = rows - 1; i >= 1; i--)

Start at rows - 1, not rows. Start at rows and the 9-star line prints twice and it looks like a stretched hexagon.

Same space/star formulas. i = 4, 3, 2, 1 → 7, 5, 3, 1 stars.

Prompt says "half". Type 5 expecting 5 lines and you'll get 9. That's the API.

Hollow diamond is the same two loops with the hollow if on stars. This file is solid.

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