Sequential Decreasing Alphabet Triangle in C

What You’ll Learn

Print a continuous alphabet sequence across rows, while each next row prints one fewer letter than the previous. Keep a running counter (k++) so the sequence goes A through O for five rows. Compare Program 22 (right-aligned growing sequential pyramid) and Program 13 (left-aligned growing sequential). Includes a live preview, worked C examples, edge cases, and complexity.

📝 Problem & Approach

Given a row count n (or fixed 5), print a left-aligned triangle of continuous alphabet letters with shrinking row lengths.

// Five rows (continuous stream; lengths 5..1)
// A B C D E
// F G H I
// J K L
// M N
// O

Inputs & Outputs

Minimal workflow

k = 'A'
for i in 1..n:
    for j from n down to i:
        print k with spacing; k++
    print newline

Approach comparison

🔮 Live Preview

Choose between 1 and 6 rows and draw the sequential decreasing triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete C programs — fixed 5 rows, scanf row count, and explicit letters-per-row count. Click View Output to reveal sample console results.

#include <stdio.h>

int main() {
    int i, j;
    char k = 'A';

    for (i = 1; i <= 5; ++i) {
        for (j = 5; j >= i; --j) {
            printf("%c ", k++);
        }
        printf("\n");
    }

    return 0;
}

A B C D E
F G H I
J K L
M N
O

#include <stdio.h>

int main() {
    int n, i, j;
    char k = 'A';

    printf("Enter number of rows (like 5): ");
    scanf("%d", &n);
    if (n < 1) return 0;

    for (i = 1; i <= n; ++i) {
        for (j = n; j >= i; --j) {
            printf("%c ", k++);
        }
        printf("\n");
    }

    return 0;
}

Enter number of rows (like 5): 3
A B C
D E
F

#include <stdio.h>

int main() {
    int n = 5;
    char k = 'A';
    int i, t, count;

    for (i = 1; i <= n; ++i) {
        count = n - i + 1;
        for (t = 0; t < count; ++t) {
            printf("%c ", k++);
        }
        printf("\n");
    }

    return 0;
}

A B C D E 
F G H I 
J K L 
M N 
O 

🔎 Worked Walkthrough — 5 rows

Trace each row’s length and the letters taken from the running counter.

Total letters: 5+4+3+2+1 = 15 (A through O).

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

Total printed letters are n+(n-1)+…+1 = n(n+1)/2, so time is O(n²).

💡 Best Practices