C++ Program to Find Smallest Number in Array

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In this article, you will learn and get code to find and print smallest element (number) from an array in C++. The size and elements for array must be entered by user at run-time. Here are the list of approaches used to create the program:

Find smallest number in an array without function and pointer
Using Pointer
Using user-defined Function

Find Smallest Number in an Array

To find the smallest element or number in an array in C++ programming, you have to ask from user to enter the size and elements for array. Now find and print the smallest one as shown in the program given below:

The question is, write a program in C++ to find and print smallest number in an array. Here is its answer:

#include<iostream>
using namespace std;
int main()
{
    int arr[100], tot, i, s;
    cout<<"Enter the Size for Array: ";
    cin>>tot;
    cout<<"Enter "<<tot<<" Array Elements: ";
    for(i=0; i<tot; i++)
        cin>>arr[i];
    s = arr[0];
    for(i=1; i<tot; i++)
    {
        if(s>arr[i])
            s = arr[i];
    }
    cout<<"\nSmallest Number = "<<s;
    cout<<endl;
    return 0;
}

This program was build and run under Code::Blocks IDE. Here is its sample run:

C++ program find smallest element in array

Now supply any number say 5 as array size, and then enter 5 numbers as 5 array elements. After supplying all these things, press ENTER key to find and print the smallest number from the array as shown in the snapshot given below:

The following statement:

s = arr[0];

supposed that the number at 0^th (very first) index is the smallest number. And then we've compared all the number at remaining indexes one by one with the number at s. If s's value is found greater than any number at any index, then we've initialized that number as new value of s.

The dry run of above program goes like:

When user enters the size say 5 for the array, then it gets stored in tot. So tot=6
Now we've created a for loop that executes 6 times. That is, the loop variable, i starts from 0 to 5
So at first time, the first number gets stored in arr[0], second number in arr[1] and so on
Therefore, if user enters 5 numbers as 5, 4, 3, 1, 2, then it gets stored in arr[] in this way:
- arr[0]=5
- arr[1]=4
- arr[2]=3
- arr[3]=1
- arr[4]=2
Now the statement that is used to suppose the first number as the smallest number. That is, arr[0] or 5 gets initialized to s
Now using the second for loop, we've compared the value of s with each and every element of arr[]
That is, at first execution of for loop, 1 gets initialized to i, and the condition i<tot or 1<5 evaluates to be true, therefore program flow goes inside the loop, and the condition s>arr[i] or 5>arr[1] or 5>4 evaluates to be true, therefore program flow goes inside the if's body and the value of arr[i] or arr[1] or 4 gets initialized to s
Now program flow goes to update part of for loop and increments the value of i. So i=2
Now the condition of for loop again gets evaluated. Every time before entering into the body of loop, condition must evaluated to be true
This time again the condition i<tot or 2<5 evaluates to be true, therefore program flow again goes inside the loop
This process continues until the condition evaluates to be false
After exiting from the loop, the variable s holds the smallest number from given list of numbers stored in arr[]
So just print the value of s as smallest number from an array entered by user

Find Smallest Number in Array using Pointer

Now let's create the same purpose program using pointer. The & is called as address of operator. Whereas * is called as value at operator.

#include<iostream>
using namespace std;
int main()
{
    int arr[100], tot, i, s, *ptr;
    cout<<"Enter the Size for Array: ";
    cin>>tot;
    cout<<"Enter "<<tot<<" Array Elements: ";
    for(i=0; i<tot; i++)
        cin>>arr[i];
    ptr = &arr[0];
    s = *ptr;
    while(*ptr)
    {
        if(s>(*ptr))
            s = *ptr;
        ptr++;
    }
    cout<<"\nSmallest Number = "<<s;
    cout<<endl;
    return 0;
}

This program produces the same output as of previous program. After executing the following statement:

ptr = &arr[0];

The address of number present at 0^th index in arr[] gets initialized to ptr. The *ptr indicates to the value present at address, that is stored in ptr. And the ptr++ is used to shift to the next index's address of the same array, arr[].

Find Smallest Number in Array using Function

This is the last program on finding the smallest element in an array. This program is created using a user-defined function named findSmallest(). This function takes an array and its size as its argument. And returns the smallest number from the array (passed as its first argument).

#include<iostream>
using namespace std;
int findSmallest(int [], int);
int main()
{
    int arr[100], tot, i, s;
    cout<<"Enter the Size for Array: ";
    cin>>tot;
    cout<<"Enter "<<tot<<" Array Elements: ";
    for(i=0; i<tot; i++)
        cin>>arr[i];
    s = findSmallest(arr, tot);
    cout<<"\nSmallest Number = "<<s;
    cout<<endl;
    return 0;
}
int findSmallest(int a[], int t)
{
    int s, i;
    s = a[0];
    for(i=1; i<t; i++)
    {
        if(s>a[i])
            s = a[i];
    }
    return s;
}

Here is its sample run with user input, 6 as array size and 10, 8, 2, 5, 7, 12 as 6 array elements:

smallest number in array using function c++

Same Program in Other Languages

C++ Online Test

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