C Program To Print 3 Numbers In Ascending Order Using If Else

Sorting numbers is a fundamental operation in programming, allowing data to be arranged in a meaningful sequence. While complex algorithms exist for large datasets, for a small, fixed number of items, simple conditional logic is often sufficient.

In this article, you will learn how to write a C program that takes three numbers as input and prints them in ascending order using if-else conditional statements.

Problem Statement

The challenge is to accept three distinct numerical inputs from a user and display them from the smallest to the largest. This requires a mechanism to compare the numbers and make decisions based on their relative values, a task perfectly suited for if-else constructs in C. The key is to cover all possible orderings of the three numbers to ensure correctness.

Example

Consider the following input and desired output:

• Input: Enter three numbers: 5, 2, 8
• Output: The numbers in ascending order are: 2, 5, 8

Background & Knowledge Prerequisites

To understand and implement the C program for sorting three numbers, familiarity with the following core C concepts is helpful:

• Basic C Program Structure: Including header files (#include ) and the main function.
• Input/Output Operations: Using printf() for displaying text and scanf() for reading user input.
• Variables and Data Types: Declaring and using integer variables (e.g., int num1;).
• Conditional Statements: Understanding if, else if, and else for decision-making logic.
• Relational Operators: Using operators like <, >, <=, >= for comparing values.

Use Cases or Case Studies

Arranging numbers in order has numerous practical applications, even for just three items:

• Ranking Data: Quickly determining the top, middle, and bottom scores in a small competition or survey.
• Simple Game Logic: Identifying the highest or lowest roll of three dice, or ordering players based on initial scores.
• Displaying Options: Presenting a range of prices, sizes, or difficulty levels in a logical sequence.
• Filtering and Validation: Ensuring that three input values adhere to a specific numerical order requirement.
• Finding Extremes: Easily identifying the minimum, maximum, and median values among three inputs without complex algorithms.

Solution Approaches

For printing three numbers in ascending order using if-else, a direct comparison method is efficient and straightforward.

Approach 1: Direct Comparison using Nested If-Else

This approach systematically compares the three numbers to identify their relative order, then prints them in the correct sequence. It involves a series of nested if-else statements to cover all possible permutations.

One-line summary

This method uses conditional logic to determine which of the three numbers is smallest, then the next smallest, and finally the largest, printing them in order.

Code example

// Sort Three Numbers in Ascending Order
#include <stdio.h>

int main() {
    // Step 1: Declare three integer variables to store the numbers
    int num1, num2, num3;

    // Step 2: Prompt the user to enter three numbers
    printf("Enter three integers: ");

    // Step 3: Read the three numbers from the user
    scanf("%d %d %d", &num1, &num2, &num3);

    // Step 4: Use if-else statements to determine the order and print
    printf("The numbers in ascending order are: ");

    if (num1 <= num2 && num1 <= num3) {
        // num1 is the smallest
        printf("%d, ", num1);
        if (num2 <= num3) {
            printf("%d, %d\\n", num2, num3);
        } else {
            printf("%d, %d\\n", num3, num2);
        }
    } else if (num2 <= num1 && num2 <= num3) {
        // num2 is the smallest
        printf("%d, ", num2);
        if (num1 <= num3) {
            printf("%d, %d\\n", num1, num3);
        } else {
            printf("%d, %d\\n", num3, num1);
        }
    } else {
        // num3 is the smallest
        printf("%d, ", num3);
        if (num1 <= num2) {
            printf("%d, %d\\n", num1, num2);
        } else {
            printf("%d, %d\\n", num2, num1);
        }
    }

    return 0;
}

Run

Sample output

Enter three integers: 17 5 32
The numbers in ascending order are: 5, 17, 32

Enter three integers: 100 20 50
The numbers in ascending order are: 20, 50, 100

Enter three integers: 7 7 2
The numbers in ascending order are: 2, 7, 7

Stepwise explanation

1. Include Header: The stdio.h header is included for standard input/output functions like printf and scanf.
2. Declare Variables: Three integer variables (num1, num2, num3) are declared to store the numbers provided by the user.
3. Get Input: The program prompts the user to enter three integers and uses scanf to read these values into the declared variables.
4. First Comparison (Finding the Smallest):

• The outermost if condition (num1 <= num2 && num1 <= num3) checks if num1 is the smallest among the three.
• If num1 is indeed the smallest, it is printed first.

1. Nested Comparison (Ordering the Remaining Two):

• Inside the first if block, a nested if (num2 <= num3) compares the remaining two numbers (num2 and num3).
• If num2 is less than or equal to num3, they are printed in the order num2, num3. Otherwise, they are printed as num3, num2.

1. Second Smallest Check:

• The else if (num2 <= num1 && num2 <= num3) block is executed if num1 was not the smallest. This checks if num2 is the smallest.
• If num2 is the smallest, it's printed first, and then num1 and num3 are compared to determine their relative order and printed.

1. Third Smallest Check:

• The final else block is executed if neither num1 nor num2 was the smallest, implying num3 must be the smallest.
• num3 is printed first, and then num1 and num2 are compared and printed in ascending order.

1. Return 0: The main function returns 0 to indicate successful execution.

Conclusion

Using if-else statements provides a clear and direct way to sort a small, fixed number of items like three integers. This method is easy to understand and implement, making it suitable for scenarios where algorithmic complexity is not a primary concern. While less scalable than loop-based sorting algorithms for larger datasets, its simplicity makes it effective for specific, limited sorting tasks.

Summary

• Read three integer values from the user.
• Employ a series of nested if-else conditions to compare the numbers.
• Identify the smallest number first, then determine the order of the remaining two.
• Print the numbers sequentially from the smallest to the largest, ensuring ascending order.