What are Number Patterns?

Number pattern programs in C require mathematical indexing to compute numbers based on current row index i and column index j.

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1. Floyd's Triangle in C

Floyd's triangle prints consecutive natural numbers in a right-angled triangular format:

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

void printFloydsTriangle(int rows) {
    int count = 1;
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= i; j++) {
            printf("%3d ", count++);
        }
        printf("\n");
    }
}

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2. Binary Alternating Triangle (0 and 1)

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

void printBinaryTriangle(int rows) {
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= i; j++) {
            /* If sum of indices (i+j) is even, print 1; else 0 */
            printf("%d ", (i + j) % 2 == 0 ? 1 : 0);
        }
        printf("\n");
    }
}

int main() {
    int rows = 5;
    printf("Floyd's Triangle (%d rows):\n", rows);
    printFloydsTriangle(rows);

    printf("\nBinary Alternating Triangle (%d rows):\n", rows);
    printBinaryTriangle(rows);
    return 0;
}

Sample Output

text (ISO Standard)
Copy
Floyd's Triangle (5 rows):
  1 
  2   3 
  4   5   6 
  7   8   9  10 
 11  12  13  14  15 

Binary Alternating Triangle (5 rows):
1 
0 1 
1 0 1 
0 1 0 1 
1 0 1 0 1 

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Complexity Analysis

• Time Complexity: O(n²) for generating $n(n+1)/2$ elements.
• Space Complexity: O(1) constant auxiliary storage.

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Related Guides

• Review star geometries in Star Pattern Programs in C.
• Master 2D nested loops in Arrays in C Programming.