C program to print pyramid star pattern or equilateral triangle star pattern

• Write a program in C to print pyramid star pattern using for loop.
• Write a C program to print an equilateral triangle star pattern of n rows using loops.

For an equilateral triangle pyramid star pattern of 5 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print pyramid star pattern using loop
In this program, we are printing a pyramid star pattern in which i^th row contains (2*i + 1) space separated stars. The index of rows and columns starts from 0.

• We first take the number of rows(R) in the pattern as input from user using scanf function.
• One iteration of outer for loop will print a row of pyramid(from i = 0 to R – 1).
• For j^th row of pyramid, the inner for loop first prints (R – i – 1) spaces for every line and then nested while loop prints (2*j + 1) stars.

Here is the matrix representation of the pyramid star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print pyramid star pattern

#include<stdio.h>
 
int main() {
    int i, j, rows, star = 0;
    printf("Enter the number of rows\n");
    scanf("%d", &rows);
 
    /* printing one row in every iteration */
    for (i = 0; i < rows; i++) {
        /* Printing spaces */
        for (j = 0; j <= (rows - i - 1); j++) {
            printf(" ");
        }
        /* Printing stars */
        while (star != (2 * i + 1)) {
            printf("*");
            star++;;
        }
        star = 0;
        /* move to next row */
        printf("\n");
    }
    return 0;
}

Output

Enter the number of rows
6
     *
    ***
   *****
  *******
 *********
***********