How to print the stars in Diamond pattern using C language?

In C programming, printing a diamond pattern with stars is a common pattern printing problem that helps understand nested loops and spacing logic. A diamond pattern consists of an upper triangular half followed by a lower triangular half.

Syntax

// Upper half pattern
for (j = 1; j <= rows; j++) {
    for (i = 1; i <= rows-j; i++)     // Print spaces
        printf(" ");
    for (i = 1; i <= 2*j-1; i++)      // Print stars
        printf("*");
    printf("<br>");
}

// Lower half pattern  
for (j = 1; j <= rows-1; j++) {
    for (i = 1; i <= j; i++)          // Print spaces
        printf(" ");
    for (i = 1; i <= 2*(rows-j)-1; i++) // Print stars
        printf("*");
    printf("<br>");
}

Understanding the Logic

The diamond pattern is created in two parts −

• Upper Half: Stars increase from 1 to maximum (2*rows-1), with decreasing leading spaces
• Lower Half: Stars decrease from maximum-2 to 1, with increasing leading spaces

Example: Complete Diamond Pattern

#include <stdio.h>

int main() {
    int rows = 5, i, j;
    
    printf("Diamond pattern with %d rows:<br><br>", rows);
    
    // Upper half of diamond
    for (j = 1; j <= rows; j++) {
        for (i = 1; i <= rows-j; i++)
            printf(" ");
        for (i = 1; i <= 2*j-1; i++)
            printf("*");
        printf("<br>");
    }
    
    // Lower half of diamond
    for (j = 1; j <= rows-1; j++) {
        for (i = 1; i <= j; i++)
            printf(" ");
        for (i = 1; i <= 2*(rows-j)-1; i++)
            printf("*");
        printf("<br>");
    }
    
    return 0;
}

Diamond pattern with 5 rows:

    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

Pattern Analysis

Key Points

• The maximum width of the diamond is 2*rows-1 stars
• Upper half uses formula: spaces = rows-j, stars = 2*j-1
• Lower half uses formula: spaces = j, stars = 2*(rows-j)-1
• Total lines printed = 2*rows-1

Conclusion

The diamond pattern demonstrates effective use of nested loops and mathematical formulas for spacing and star count. Understanding this pattern helps in solving more complex pattern printing problems in C programming.