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Loop Programs in C

Print Inverted Number Pyramid Pattern

Introduction

An Inverted Number Pyramid displays numbers in decreasing order of rows.
Each row starts with 1 and goes up to the current row limit, but the total number of rows decreases from n to 1.

For example, for n = 5:

                          1  2  3  4  5

                            1  2  3  4

                              1  2  3

                                1  2

                                  1

This pattern teaches reverse looping, space management, and nested loop structure.

C Program: Print Inverted Number Pyramid Pattern

Method 1: Using for loop

#include <stdio.h>
 
int main() {
    int n;
    printf("Enter number of rows: ");
    scanf("%d", &n);
 
    for (int i = n; i >= 1; i--) {
        // Print leading spaces
        for (int j = i; j < n; j++) {
            printf(" ");
        }
 
        // Print numbers
        for (int k = 1; k <= i; k++) {
            printf("%d ", k);
        }
 
        printf("\n");
    }
 
    return 0;
}

 
OUTPUT :
Enter number of rows: 5
1 2 3 4 5
 1 2 3 4
  1 2 3
   1 2
    1

Explanation

1. The outer loop runs from n down to 1.
2. The first inner loop prints spaces for alignment.
3. The second inner loop prints numbers from 1 to the current row limit (i).
4. Each subsequent row prints one less number than the previous row.

C Program: Print Inverted Number Pyramid Pattern

Method 2: Using while loop

#include <stdio.h>
 
int main() {
    int n, i, j, k;
    printf("Enter number of rows: ");
    scanf("%d", &n);
 
    i = n;
    while (i >= 1) {
        j = i;
        while (j < n) {
            printf(" ");
            j++;
        }
 
        k = 1;
        while (k <= i) {
            printf("%d ", k);
            k++;
        }
 
        printf("\n");
        i--;
    }
 
    return 0;
}

 
OUTPUT :
Enter number of rows: 5
1 2 3 4 5
 1 2 3 4
  1 2 3
   1 2
    1

Explanation

1. The outer loop runs from n down to 1.
2. The first inner loop prints spaces for alignment.
3. The second inner loop prints numbers from 1 to the current row limit (i).
4. Each subsequent row prints one less number than the previous row.

C Program: Print Inverted Number Pyramid Pattern

Method 3: Using do..while loop

#include <stdio.h>
 
int main() {
    int n, i, j, k;
    printf("Enter number of rows: ");
    scanf("%d", &n);
 
    i = n;
    do {
        j = i;
        do {
            if (j < n)
                printf(" ");
            j++;
        } while (j <= n);
 
        k = 1;
        do {
            if (k <= i)
                printf("%d ", k);
            k++;
        } while (k <= i);
 
        printf("\n");
        i--;
    } while (i >= 1);
 
    return 0;
}

 
OUTPUT :
Enter number of rows: 5
1 2 3 4 5
 1 2 3 4
  1 2 3
   1 2
    1

Explanation

1. The outer loop runs from n down to 1.
2. The first inner loop prints spaces for alignment.
3. The second inner loop prints numbers from 1 to the current row limit (i).
4. Each subsequent row prints one less number than the previous row.