Java program to find second largest number in an array

If you want to practice data structure and algorithm programs, you can go through data structure and algorithm interview questions.
In this post, we will see how to find second largest number in an array.

Problem :

Given an unsorted array, you need to find second largest element in the array in o(n) time complexity.
For example:
int[] arr1={7,5,6,1,4,2};
Second largest element in the array : 6

Solution:

You can sort the array and then return second last element in the array but it will be done in o(nlogn) time,

Algorithm:

  • Initialize highest and secondHighest with minimum possible value.
  • Iterate over array.
  • If current element is greater than highest
    • Assign secondHighest = highest
    • Assign highest = currentElement
  • Else if current element is greater than secondHighest 
    • Assign secondHighest =current element.

Java Program to find second largest number in array:

Create a main java class named "FindSecondLargestMain.java".
package org.arpit.java2blog;

public class FindSecondLargestMain {
 public static void main(String args[])
 {
  int[] arr1={7,5,6,1,4,2};
  int secondHighest=findSecondLargestNumberInTheArray(arr1);
  System.out.println("Second largest element in the array : "+ secondHighest);
 }
 
 public static int findSecondLargestNumberInTheArray(int array[])
 {
  // Initialize these to the smallest value possible
  int highest = Integer.MIN_VALUE;
  int secondHighest = Integer.MIN_VALUE;

  // Loop over the array
  for (int i = 0; i < array.length; i++) {

    // If current element is greater than highest
      if (array[i] > highest) {

          // assign second highest element to highest element 
          secondHighest = highest;

          //  highest element to current element
          highest = array[i];
      } else if (array[i] > secondHighest)
          // Just replace the second highest
          secondHighest = array[i];
      }
  

  // After exiting the loop, secondHighest now represents the second
  // largest value in the array
 return secondHighest;
 }
}
When you run above program, you will get below output:
Second largest element in the array : 6

Written by Arpit:

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