Understanding Nested Loops for Patterns

Printing star patterns in C reinforces understanding of nested loops. The outer loop controls the rows, while inner loops control spacing and character printing across columns.

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1. Right-Angled Star Triangle

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>

void printRightTriangle(int rows) {
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= i; j++) {
            printf("* ");
        }
        printf("\n");
    }
}

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2. Centered Pyramid Pattern

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>

void printPyramid(int rows) {
    for (int i = 1; i <= rows; i++) {
        /* Print leading spaces */
        for (int space = 1; space <= rows - i; space++) {
            printf("  ");
        }
        /* Print odd number of stars: (2*i - 1) */
        for (int k = 1; k <= (2 * i - 1); k++) {
            printf("* ");
        }
        printf("\n");
    }
}

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3. Diamond Star Pattern

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>

void printDiamond(int n) {
    /* Upper half of diamond */
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n - i; j++) printf(" ");
        for (int j = 1; j <= 2 * i - 1; j++) printf("*");
        printf("\n");
    }
    /* Lower inverted half */
    for (int i = n - 1; i >= 1; i--) {
        for (int j = 1; j <= n - i; j++) printf(" ");
        for (int j = 1; j <= 2 * i - 1; j++) printf("*");
        printf("\n");
    }
}

int main() {
    int n = 4;
    printf("Centered Star Pyramid (n=%d):\n", n);
    printPyramid(n);

    printf("\nStar Diamond Pattern (n=%d):\n", n);
    printDiamond(n);
    return 0;
}

Sample Output

text (ISO Standard)
Copy
Centered Star Pyramid (n=4):
      * 
    * * * 
  * * * * * 
* * * * * * * 

Star Diamond Pattern (n=4):
   *
  ***
 *****
*******
 *****
  ***
   *

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Complexity Analysis

• Time Complexity: O(n²) quadratic time across row and column iterations.
• Space Complexity: O(1) zero extra memory allocations.

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Related Programs

• Explore numerical grids in Number Pattern Programs in C.
• Try combinatorial printing in Pascal's Triangle in C.