Reverse Ascending Number Triangle in C

What You’ll Learn

Program 6 prints a reverse ascending number triangle: each row adds one digit on the left until the last row shows 1..rows — the mirror companion to Program 5’s growing triangle. This tutorial covers the shape rule, descending outer loop, inner bound i..rows, a live preview, worked C examples, edge cases, and complexity.

📝 Problem & Approach

Given row count rows = 5, print a reverse ascending number triangle — row outer index i shows digits i..rows.

// rows = 5
//5
//45
//345
//2345
//12345

Inputs & Outputs

Minimal workflow

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

Approach comparison

🔮 Live Preview

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

Press "Draw pattern".

Examples Gallery

Three complete C programs — fixed rows, user input, and a compact trace with rows = 3. 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 <= rows; j++)
            printf("%d", j);

        printf("\n");
    }

    return 0;
}

5
45
345
2345
12345

#include <stdio.h>

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

    printf("Enter the number of rows: ");
    if (scanf("%d", &rows) != 1 || rows < 1)
        return 1;

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

        printf("\n");
    }

    return 0;
}

Enter the number of rows: 4
4
34
234
1234

#include <stdio.h>

int main() {
    int rows = 3;
    int i, j;

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

        printf("\n");
    }

    return 0;
}

3
23
123

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop value of i (counting down) and count how many digits the inner loop prints.

Total digit prints: 1 + 2 + 3 + 4 + 5 = 15 = 5×6/2.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices