C program to Find the Largest Number Among Three Numbers

Given three numbers A, B and C; The task is to find the largest number among the three. Examples:

Input: A = 2, B = 8, C = 1
Output: Largest number = 8

Input: A = 231, B = 4751, C = 75821
Output: Largest number = 75821

In the below programs, to find the largest of the three number, , , and ‘s are used. Algorithm to find the largest of three numbers:

1. Start
2. Read the three numbers to be compared, as A, B and C.
3. Check if A is greater than B.

  3.1 If true, then check if A is greater than C.
    3.1.1 If true, print 'A' as the greatest number.
    3.1.2 If false, print 'C' as the greatest number.

  3.2 If false, then check if B is greater than C.
    3.1.1 If true, print 'B' as the greatest number.
    3.1.2 If false, print 'C' as the greatest number.
4. End

FlowChart to find the largest of three numbers: Below is the C program to find the largest among the three numbers: Example 1: Using only if statements to find the largest number. 

C

#include <stdio.h>

int main()
{
    int A, B, C;

    printf("Enter the numbers A, B and C: ");
    scanf("%d %d %d", &A, &B, &C);

    if (A >= B && A >= C)
        printf("%d is the largest number.", A);

    if (B >= A && B >= C)
        printf("%d is the largest number.", B);

    if (C >= A && C >= B)
        printf("%d is the largest number.", C);

    return 0;
}

Output:

Enter the numbers A, B and C: 2 8 1 
8 is the largest number.

Time complexity: O(1) as it is doing constant operations
Auxiliary space: O(1)

Example 2: Using if-else statement to find the largest number. 

C

#include <stdio.h>
int main()
{
    int A, B, C;

    printf("Enter three numbers: ");
    scanf("%d %d %d", &A, &B, &C);

    if (A >= B) {
        if (A >= C)
            printf("%d is the largest number.", A);
        else
            printf("%d is the largest number.", C);
    }
    else {
        if (B >= C)
            printf("%d is the largest number.", B);
        else
            printf("%d is the largest number.", C);
    }

    return 0;
}

Output:

Enter the numbers A, B and C: 2 8 1 
8 is the largest number.

Time complexity: O(1) as it is doing constant operations
Auxiliary space: O(1)

Example 3: Using nested if-else statements to find the largest number. 

C

#include <stdio.h>
int main()
{
    int A, B, C;

    printf("Enter three numbers: ");
    scanf("%d %d %d", &A, &B, &C);

    if (A >= B && A >= C)
        printf("%d is the largest number.", A);

    else if (B >= A && B >= C)
        printf("%d is the largest number.", B);

    else
        printf("%d is the largest number.", C);

    return 0;
}

Output:

Enter the numbers A, B and C: 2 8 1 
8 is the largest number.

Time complexity: O(1) as it is doing constant operations
Auxiliary space: O(1)

Example 4: Using Ternary operator to find the largest number. 

C

#include <stdio.h>
int main()
{
    int A, B, C, largest;

    printf("Enter three numbers: ");
    scanf("%d %d %d", &A, &B, &C);

    largest = A > B ? (A > C ? A : C) : (B > C ? B : C);

    printf("%d is the largest number.", largest);

    return 0;
}

Output:

Enter the numbers A, B and C: 2 8 1 
8 is the largest number.

Time complexity: O(1) as it is doing constant operations
Auxiliary space: O(1)