C program to find maximum of four integers by defining function

In C programming, we can find the maximum of four integers by defining our own function. We create a max() function that compares two numbers and returns the larger one, then use it repeatedly to find the maximum among all four numbers.

So, if the input is like a = 5, b = 8, c = 2, d = 3, then the output will be 8.

Syntax

int max(int x, int y);

Algorithm

To solve this, we will follow these steps −

• Define a function max() that takes two integers x and y
• Return the maximum of x and y
• Take four numbers a, b, c, and d
• Find left_max = max(a, b)
• Find right_max = max(c, d)
• Find final_max = max(left_max, right_max)
• Return or print the final maximum

Example

Let us see the following implementation to get better understanding −

#include <stdio.h>

int max(int x, int y) {
    if (x > y) {
        return x;
    } else {
        return y;
    }
}

int main() {
    int a = 5, b = 8, c = 2, d = 3;
    int left_max = max(a, b);
    int right_max = max(c, d);
    int final_max = max(left_max, right_max);
    
    printf("Numbers: a=%d, b=%d, c=%d, d=%d
", a, b, c, d);
    printf("Maximum number is: %d
", final_max);
    
    return 0;
}

Numbers: a=5, b=8, c=2, d=3
Maximum number is: 8

Alternative Approach: Single Function Call

We can also find the maximum in a single nested function call −

#include <stdio.h>

int max(int x, int y) {
    return (x > y) ? x : y;
}

int main() {
    int a = 10, b = 25, c = 15, d = 8;
    int maximum = max(max(a, b), max(c, d));
    
    printf("Numbers: a=%d, b=%d, c=%d, d=%d
", a, b, c, d);
    printf("Maximum number is: %d
", maximum);
    
    return 0;
}

Numbers: a=10, b=25, c=15, d=8
Maximum number is: 25

Key Points

• The max() function can be reused for any number comparison
• We can use the ternary operator ?: for a more concise comparison
• The approach requires exactly 3 function calls to find maximum of 4 numbers

Conclusion

Using a user−defined max() function provides a clean and reusable solution to find the maximum of four integers. This modular approach makes the code more readable and maintainable.