Java Program to Find Second Smallest Number in an Array

Write a java program to find second smallest number in an array without sorting. Given an unsorted array of integers, we have to write a code to find second smallest number without sorting an array.

If we use sorting then the time complexity of an algorithm is O(nlogn). You can read about various sorting algorithms and their time complexity.

We can solve this problem in a single traversal in O(n) time complexity.

C program to find second smallest number in an array without sorting

Java Program to Find Second Smallest Number in an Array

Let's write a java code to find second smallest number in an array in a single traversal. The time complexity of this approach is O(n).

import java.util.Scanner;

public class secondSmallest {

  public static void main(String[] args) {

    Scanner in = new Scanner(System.in);

    //Input size of an array
    System.out.println("Enter the size of an array");
    int n = in.nextInt();

    //Array declaration
    int arr[] = new int[n];

    System.out.println("Enter an array elements");

    //Taking an input value of an array
    for (int j = 0; j < arr.length; j++) {
       arr[j] = in.nextInt();
    }
    
    //Initialize with max value of integer
    int smallest = Integer.MAX_VALUE;
    int secondSmallest = Integer.MAX_VALUE;

    //Traverse an array
    for (int i = 0; i < arr.length; i++) {

      if (smallest > arr[i]) {
         secondSmallest = smallest;
         smallest = arr[i];

     }

     if (arr[i] > smallest && arr[i] < secondSmallest) {
        secondSmallest = arr[i];
     }
   }
   
   System.out.println("Second smallest number is " + secondSmallest);
 }

}

Output -

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