Reverse Descending Number Triangle in C

What You’ll Learn

The reverse descending number triangle prints 54321, 4321, 321, 21, 1 — a natural step after the left-shifted triangle in Program 2. This tutorial covers descending outer and inner loops, a live preview, algorithm steps, worked C examples, edge cases, and complexity.

📝 Problem & Approach

Given a positive integer rows (e.g. 5), print a reverse descending triangle: each row i shows digits from i down to 1, with the outer loop counting from rows down to 1.

// rows = 5 (conceptual shape)
// 54321
// 4321
// 321
// 21
// 1

Inputs & Outputs

Minimal workflow

for i from rows down to 1:
    for j from i down to 1:
        print j
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 3 and 9 and draw the reverse descending triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete C programs — fixed rows, user input, and spaced output variant. Click View Output to reveal sample console results.

#include <stdio.h>

int main() {
    int rows = 5;
    int i, j;

    for (i = rows; i >= 1; --i) {
        for (j = i; j >= 1; --j)
            printf("%d", j);

        printf("\n");
    }

    return 0;
}

54321
4321
321
21
1

#include <stdio.h>

int main() {
    int rows;
    int i, j;

    printf("Enter the number of rows: ");
    scanf("%d", &rows);

    for (i = rows; i >= 1; --i) {
        for (j = i; j >= 1; --j)
            printf("%d", j);

        printf("\n");
    }

    return 0;
}

Enter the number of rows: 4
4321
321
21
1

#include <stdio.h>

int main() {
    int rows = 5;
    int i, j;

    for (i = rows; i >= 1; --i) {
        for (j = i; j >= 1; --j)
            printf("%d ", j);

        printf("\n");
    }

    return 0;
}

5 4 3 2 1 
4 3 2 1 
3 2 1 

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop value of i, the inner-loop range, digit count, and full row output.

Prints per row = i — total prints = n(n+1)/2 for n rows.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices