Mixed Number Triangle in C++

What You’ll Learn

Program 50 prints a mixed number triangle: each row combines descending i..2 with ascending 1..(rows-i+1) — a natural step after Program 49’s multiplication triangle. This tutorial covers two inner loops per row, a live preview, worked C++ examples, edge cases, and complexity.

📝 Problem & Approach

Given row count rows = 5, print a mixed number triangle — row i shows descending i..2 then ascending 1..(rows-i+1).

// rows = 5
//12345
//21234
//32123
//43212
//54321

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    for j from i down to 2:
        print j
    for k from 1 to (rows - i + 1):
        print k
    print newline

Approach comparison

🔮 Live Preview

Choose row count between 3 and 9 and draw the mixed number triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete C++ programs — fixed rows, user input, and a compact trace demo. Click View Output to reveal sample console results.

#include <iostream>
using namespace std;

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

    for (i = 1; i <= rows; i++) {
        for (j = i; j > 1; j--)
            cout << j;

        for (k = 1; k <= rows + 1 - i; k++)
            cout << k;

        cout << "\n";
    }

    return 0;
}

12345
21234
32123
43212
54321

#include <iostream>
using namespace std;

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

    cout << "Enter the number of rows: ";
    cin >> rows;
    if (cin.fail() || rows < 1)
        return 1;

    for (i = 1; i <= rows; i++) {
        for (j = i; j > 1; j--)
            cout << j;

        for (k = 1; k <= rows + 1 - i; k++)
            cout << k;

        cout << "\n";
    }

    return 0;
}

Enter the number of rows: 4
1234
2123
3212
4321

#include <iostream>
using namespace std;

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

    for (i = 1; i <= rows; i++) {
        for (j = i; j > 1; j--)
            cout << j;

        for (k = 1; k <= rows + 1 - i; k++)
            cout << k;

        cout << "\n";
    }

    return 0;
}

123
212
321

🔎 Worked Walkthrough — rows = 5

Trace each row’s descending and ascending halves and the full line output.

Each row prints exactly rows digits — descending count plus ascending count always equals rows.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices