C Program to Find Smallest of Three Numbers

Here we will learn about how to find and print smallest among any given three numbers (by user at run-time) with and without using any user-defined function. At last of the tutorial, we will also see how to find out and print the smallest of three numbers using Ternary operator.

Find Smallest of Three Numbers in C

Here is the program that will find out the smallest of three numbers provided by user at run-time.

#include<stdio.h>
#include<conio.h>
int main()
{
    int a, b, c, small;
    printf("Enter three numbers : ");
    scanf("%d%d%d", &a, &b, &c);
    if(a<b)
    {
        if(b<c)
            small = a;
        else
        {
            if(a<c)
                small = a;
            else
                small = c;
        }
    }
    else
    {
        if(b<c)
            small = b;
        else
            small = c;
    }
    printf("\nSmallest number is: %d", small);
    getch();
    return 0;
}

The program was written under Code::Blocks IDE, here is the first snapshot of the sample run after successful build and run:

c find smallest among three numbers

Supply any three numbers and press ENTER key to see the smallest number among the given three numbers as shown here in the snapshot given below:

find smallest of three numbers c

Here are some of the main steps used in above program:

  • Receive any three numbers as input say 10, 20, and 30 inside the three variables say a, b, and c
  • Use if block and check whether value of a is less than b or not
  • If it is, then inside the if block, create another if block and check whether b is less than c
    • If it is, then initialize the value of a to any variable say small
    • Otherwise, check whether a is less than c or not
      • If it is, then initialize a to small
      • Otherwise, initialize c to small
  • Now come out from the if block and enter into the else block (in case if a is not less than b)
  • Check whether b is less than c or not
  • If it is, then initialize b to small
  • Otherwise, initialize c to small
  • Now whatever the smallest value is, small holds it
  • Therefore, just print the value of small variable

Here is another program to find out the smallest of any three numbers in too simple way. This program is simple and easy to understand:

#include<stdio.h>
#include<conio.h>
int main()
{
    int a, b, c, small;
    printf("Enter three numbers : ");
    scanf("%d%d%d", &a, &b, &c);
    if(a<b && a<c)
        small = a;
    else if(b<a && b<c)
        small = b;
    else
        small = c;
    printf("\nSmallest number is: %d", small);
    getch();
    return 0;
}

Here is the final snapshot of the above program's sample run:

c print smallest of three numbers

In above program, we have check that whether first number say a is less than both the other number say b and c or not. If it is, then we have initialized the value of a to small. In this way, we have used the logic to find out the smallest of three numbers in simple way.

C Find Smallest of Three Numbers using Function

Let's create another program that will do the same task as the above two program has done but using user-defined function. Here is the program that uses a user-defined function to return the smallest among any three numbers:

#include<stdio.h>
#include<conio.h>
int getSmall(int, int, int);
int main()
{
    int a, b, c, small;
    printf("Enter three numbers : ");
    scanf("%d%d%d", &a, &b, &c);
    small = getSmall(a, b, c);
    printf("\nSmallest = %d", small);
    getch();
    return 0;
}
int getSmall(int num1, int num2, int num3)
{
    if(num1<num2)
    {
        if(num2<num3)
            return num1;
        else
        {
            if(num1<num3)
                return num1;
            else
                 return num3;
        }
    }
    else
    {
        if(num2<num3)
            return num2;
        else
            return num3;
    }
}

Here is the final snapshot of the sample run:

c find smallest of three using function

C Find Smallest of Three Numbers using Ternary Operator

Let's create another program that will also find and print the smallest of three numbers but this time using Ternary operator as shown in the program given below:

#include<stdio.h>
#include<conio.h>
int main()
{
    int a, b, c, small;
    printf("Enter three numbers : ");
    scanf("%d%d%d", &a, &b, &c);
    small = (a<b) ? (a<c?a:c) : (b<c?b:c);
    printf("\nSmallest = %d", small);
    getch();
    return 0;
}

Here is the final snapshot of the sample run:

print smallest of three using ternary c

The main logical code is:

small = (a<b) ? (a<c?a:c) : (b<c?b:c);

The description of above one line logical code is given below:

  • Here is the expression a<b returns to be true
    • then the expression a<c?a:c gets run. If this will run, then if a<c returns to be true
      • then a replaces whole expression and will be initialized to small
      • otherwise c replaces whole expression and will be initialized to small
    • otherwise the expression, b<c?b:c gets run. If this will run, then if b<c returns to be true
      • then b replaces whole expression and will be initialized to small
      • otherwise c replaces whole expression and will be initialized to small
  • Here we have used nested ternary operator, that is ternary operator inside ternary operator to find out smallest among three numbers
  • For example, let the input value of a, b, and c is 30, 20, and 10
  • Therefore, the expression a<b or 30<20 returns to be false, then the expression b<c?b:c gets run
  • And as b<c or 20<10 also returns to be false, therefore c will be the final value of the whole expression
  • Therefore, the value of c say 10 will be initialized to small
  • Print the value of small

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