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C program to find two smallest elements in a one dimensional array

In this article we are going to implement a C program to find two smallest elements in a one dimensional array.
Submitted by Radib Kar, on December 10, 2018

Problem statement

Write a C program to find two smallest elements in a one dimensional array.

Example: Type1: (all the elements are not same & no of element is more than two)

    Array size: 4
    Elements: 32 54 -6 43
    Output: -6 32

Example: Type2: (second minimum doesn’t exist as size of array < 2)

    Array size : 1
    Elements: 4
    Output: 4

Example: Type3: (all elements are same, thus only one smallest element)

    Array size : 4
    Elements: 13 13 13 13
    Output: 13

Algorithm

1. Define two variable min & sec_min
2. Initialize min to array[0] & sec_min to INT_MAX
3. Scan the entire array

For(int i=0;i<n;i++)
    if array[i]<min
        then update min to array[i]&sec_min to previousmin value
    else if array[i] is lesser than sec_min but greater than min
        then update sec_min to array value
        do nothing to min
End for loop

4. If still sec_min has the value INT_MAX
   Only one smallest value exists, print it
   Else
   Print min & sec_min

C implementation to find two smallest elements in a one dimensional array

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

void findTwoMin(int* a,int n){

	int min=a[0]; //initialize min to first array element
	int sec_min=INT_MAX,temp=0; //initialize second min to INT_MAX

	for(int i=0;i<n;i++){ //scan the entire array
		//if a[i]< min then update min to array value 
		//& second min to previous min value 
		if(a[i]<min){
			sec_min=min;
			min=a[i];
		}
		//else if a[i] is lesser than second min but 
		//greater than min then update second min to array value
		else if (a[i] < sec_min && a[i] > min) 
			sec_min=a[i];
		//do nothing to min
	}
	
	//if second min is still at its initialized value 
	//then no second minimum exists at all
	if(sec_min==INT_MAX)
		printf("only one smallest element: %d ",min);
	else
		printf("First smallest element: %d  & second smallest element : %d",min,sec_min);
}

int main(){
	int n;

	printf("enter no of elements\n");
	scanf("%d",&n);
	
	//dynamic array created
	int *a=(int*) malloc(sizeof(int)*n);
	
	printf("enter the elements........\n");
	//taking input
	for(int i=0;i<n;i++)
		scanf("%d",&a[i]);
	
	//find two smallest no
	findTwoMin(a,n);

	return 0;
}

Output (Type1 example)

enter no of elements
4
enter the elements........
32 54 -6 43
First smallest element: -6  & second smallest element : 32

Output (Type2 example)

enter no of elements
1
enter the elements........
4
only one smallest element: 4 

Output (Type3 example)

enter no of elements
4
enter the elements........
13 13 13 13
only one smallest element: 13

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