This C program takes three characters and an integer `n`...

August 18, 2025 at 06:46 AM

#include <stdio.h>

int main() {
    char ch[3];
    int n, i, j, space;
    int k = 0; 

    // Read characters and n
    printf("Enter 3 characters: ");
    for (i = 0; i < 3; i++) {
        scanf(" %c", &ch[i]);
    }
    printf("Enter n: ");
    scanf("%d", &n);

    for (i = 1; i <= n; i++) {
        for (space = 1; space <= n - i; space++) {
            printf(" ");
        }

        //row
        for (j = 1; j <= (2 * i - 1); j++) {
            if (j == 1 || j == (2 * i - 1)) {
                printf("%c", ch[k % 3]);
                k++;
            } else {
                printf(" ");
            }
        }
        printf("\n");
    }

    for (i = n - 1; i >= 1; i--) {
        for (space = 1; space <= n - i; space++) {
            printf(" ");
        }

        for (j = 1; j <= (2 * i - 1); j++) {
            if (j == 1 || j == (2 * i - 1)) {
                printf("%c", ch[k % 3]);
                k++;
            } else {
                printf(" ");
            }
        }
        printf("\n");
    }

    return 0;
}

This C program takes three characters and an integer n from the user, and then creates a diamond-shaped pattern made of these characters. The program follows these steps:

Step-by-step breakdown:

Input Collection
- The user is prompted to enter three characters (ch[0], ch[1], ch[2]).
- The user is then prompted to enter an integer n, which represents the number of rows in the upper half of the diamond (excluding the middle).
Diamond Pattern Logic
- The diamond shape is constructed in two parts:
  - Upper part (including the middle row)
  - Lower part (inverted version of the upper part, excluding the middle row)

Upper Part Construction

For i from 1 to n (inclusive):
- Print leading spaces (n - i).
- Print characters to form an upward triangle. The number of characters on row i is (2 * i - 1):
  - Only the first (j == 1) and the last positions (j == 2 * i - 1) on each row are filled with characters from the ch[] array, following a cyclic order (k % 3, where k ensures the cycling between ch[0], ch[1], ch[2]).
  - All other positions are filled with spaces.

Lower Part Construction

For i from n - 1 down to 1 (inclusive):
- Similar to the upper part, except the rows decrease in size to create the bottom half of the diamond.

Output
- The result is a diamond consisting of the three characters in cyclic order, creating a frame of characters with spaces inside.

Example Input/Output

Input:

If the user enters:
```
Enter 3 characters: A B C
Enter n: 4
```

Output:

The program generates:

   A
  B C
 A   B
C     A
 B   C
  A B
   C

Explanation of Output

Each row:
- Includes leading spaces for alignment towards the center.
- Characters are printed on the edges of the diamond rows, cycling through A, B, C.
- Spaces are used in the middle where characters are not present.

Key Observations

k % 3: Ensures characters cycle through the array ch[] (e.g., A, B, C, A, B, C,...).
The diamond pattern consists of symmetrical rows, and the program constructs the top and bottom sections separately.

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