Rotating Alphabet Pattern in C

What You’ll Learn

Each row is a cyclic-style rotation of the same set of letters: print from the row start to E, then wrap by printing the earlier letters in reverse (without duplicating the boundary letter). This output uses adjacent letters (no spaces), matching the reference. Compare Program 25 (shrinking sequential stream) and Program 18 (palindrome halves). Includes a live preview, worked C examples, edge cases, and complexity.

📝 Problem & Approach

Given a top letter (or fixed E), print n fixed-length rotating rows from A through that top letter.

// Five rows (adjacent letters; fixed length 5)
// ABCDE
// BCDEA
// CDEBA
// DECBA
// EDCBA

Inputs & Outputs

Minimal workflow

for i from 0 to n-1:          // or 'A'..top
    for j from i to n-1:      // forward to top
        print letter[j]
    for k from i down to 1:   // wrap earlier letters
        print letter[k - 1]
    print newline

Approach comparison

🔮 Live Preview

Choose a top letter from A to F and draw the rotating alphabet pattern in the browser.

Press "Draw pattern".

Examples Gallery

Three complete C programs — fixed A–E, scanf top letter, and a char-array rewrite. Click View Output to reveal sample console results.

#include <stdio.h>

int main() {
    char i, j, k;

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

    return 0;
}

ABCDE
BCDEA
CDEBA
DECBA
EDCBA

#include <stdio.h>

int main() {
    char top, i, j, k;

    printf("Enter top letter (like E): ");
    scanf(" %c", &top);

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

    return 0;
}

Enter top letter (like E): D
ABCD
BCDA
CDBA
DCBA

#include <stdio.h>
#include <string.h>

int main() {
    char letters[] = "ABCDE";
    int n = (int)strlen(letters);
    int i, j, k;

    for (i = 0; i < n; ++i) {
        for (j = i; j < n; ++j) {
            printf("%c", letters[j]);
        }
        for (k = i - 1; k >= 0; --k) {
            printf("%c", letters[k]);
        }
        printf("\n");
    }

    return 0;
}

ABCDE
BCDEA
CDEBA
DECBA
EDCBA

🔎 Worked Walkthrough — A–E

Trace each row’s forward run, reverse wrap, and full line.

Every row length is 5. Note the wrap is reverse of the prefix (so row 3 is CDEBA, not CDEAB).

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

For n letters, each of n rows prints n characters, so total work is O(n²).

💡 Best Practices