C++ Program To Find Largest Number Among Three Numbers Using If Statement

Finding the largest number among a set of values is a fundamental programming task. It involves comparing numbers and determining which one holds the maximum value. In this article, you will learn how to write a C++ program to find the largest among three numbers using only if statements, a core conditional control structure.

Problem Statement

In many computational scenarios, there's a need to identify the maximum value from a given set of numbers. Specifically, we aim to address the problem of comparing three distinct numbers and correctly identifying which one is the largest. This task forms the basis for more complex data analysis and sorting algorithms.

Example

Consider the numbers 10, 25, and 15. The program should identify 25 as the largest number.

Input: num1 = 10 num2 = 25 num3 = 15

Expected Output: The largest number is: 25

Background & Knowledge Prerequisites

To understand this article, readers should have a basic understanding of:

• C++ Syntax: How to declare variables, use basic data types (like int), and perform input/output operations.
• if Statement: The concept of conditional execution using if, else if, and else blocks.
• Comparison Operators: Operators like >, <, >=, <=, ==, != for comparing values.

No specific libraries beyond are required for this problem.

Use Cases or Case Studies

Identifying the largest number has several practical applications:

• Finding the Highest Score: In an educational system, determining the highest score among three students in a particular subject.
• Identifying Peak Performance: Comparing performance metrics from three different servers or machines to find the best performing one.
• Selecting the Maximum Bid: In an auction system, finding the highest bid among three participants to declare the winner.
• Resource Allocation: Deciding which of three available resources has the most capacity or is least utilized.
• Financial Analysis: Pinpointing the highest stock price observed over three different periods.

Solution Approaches

While multiple ways exist to find the largest number, we will focus on using if statements due to their fundamental role in conditional logic.

Approach 1: Using Nested if-else if-else Statements

This approach uses a series of if, else if, and else statements to compare the numbers systematically.

One-line summary: Compare the first number with the second and third, then compare the remaining two if the first isn't the largest.

// Find Largest Number Among Three
#include <iostream> // Required for input/output operations
using namespace std; // Use standard namespace

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
    cout << "Enter three numbers: ";

    // Step 3: Read the three numbers from the user
    cin >> num1 >> num2 >> num3;

    // Step 4: Use if-else if-else to find the largest number
    if (num1 >= num2 && num1 >= num3) {
        // If num1 is greater than or equal to both num2 and num3, then num1 is the largest
        cout << "The largest number is: " << num1 << endl;
    } else if (num2 >= num1 && num2 >= num3) {
        // If num2 is greater than or equal to both num1 and num3, then num2 is the largest
        cout << "The largest number is: " << num2 << endl;
    } else {
        // If neither num1 nor num2 is the largest, then num3 must be the largest
        cout << "The largest number is: " << num3 << endl;
    }

    return 0; // Indicate successful program execution
}

Run

Sample Output:

Enter three numbers: 45 12 78
The largest number is: 78

Stepwise Explanation:

1. Include Header and Namespace: The header is included for standard input (cin) and output (cout). using namespace std; simplifies the use of these functions.
2. Declare Variables: Three integer variables (num1, num2, num3) are declared to store the numbers provided by the user.
3. User Input: The program prompts the user to enter three numbers, which are then read into the declared variables using cin.
4. First if Condition: if (num1 >= num2 && num1 >= num3) checks if num1 is greater than or equal to both num2 and num3. If this condition is true, num1 is the largest, and its value is printed. The && (logical AND) operator ensures both comparisons must be true.
5. else if Condition: If the first if condition is false, the program moves to the else if (num2 >= num1 && num2 >= num3) block. This checks if num2 is greater than or equal to both num1 and num3. If true, num2 is printed as the largest.
6. else Block: If both previous conditions are false, it implies that num3 must be the largest number, as it wasn't smaller than both num1 and num2 in the previous checks. The else block then prints num3.
7. Return 0: return 0; signals that the program executed successfully.

Conclusion

By leveraging the power of if statements, we can effectively compare three numbers and determine the largest among them. This fundamental logic forms the backbone of decision-making processes in programming, allowing programs to respond dynamically to different input values. The nested if-else if-else structure provides a clear and robust way to handle multiple comparison scenarios.

Summary

• The problem involves comparing three numbers to identify the one with the highest value.
• Basic C++ syntax, if statements, and comparison operators are essential prerequisites.
• The if-else if-else structure systematically compares numbers to find the maximum.
• The && (logical AND) operator is crucial for checking multiple conditions simultaneously.
• This logic has broad applications, from finding highest scores to selecting peak performance metrics.