Second largest element in the array

Posted: 13 Nov, 2020
Difficulty: Easy

PROBLEM STATEMENT

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You have been given an array/list 'ARR' of integers. Your task is to find the second largest element present in the 'ARR'.

Note:
a) Duplicate elements may be present.

b) If no such element is present return -1.
Example:
Input: Given a sequence of five numbers 2, 4, 5, 6, 8.

Output:  6

Explanation:
In the given sequence of numbers, number 8 is the largest element, followed by number 6 which is the second-largest element. Hence we return number 6 which is the second-largest element in the sequence.
Input format:
The first line of input contains an integer ‘T’ denoting the number of test cases. 

The next ‘2*T’ lines represent the ‘T’ test cases.

The first line of each test case contains an integer ‘N’ denoting the number of elements in the array.

The second line of each test case contains ‘N’ space-separated integers denoting the elements in the array. 
Output Format:
For each test case, print a single line containing a single integer denoting the second largest element in the array.

The output of each test case will be printed in a separate line.
Note:
You are not required to print the expected output; it has already been taken care of, Just implement the function.
Constraints:
1 <= T <= 100
1 <= N <= 5000
-10 ^ 9 <= 'SIZE' <= 10 ^ 9 

Where ‘T’ is the total number of test cases, ‘N’ denotes the number of elements in the array and ‘SIZE’ denotes the range of the elements in the array.

Time limit: 1 sec.
Approach 1

The idea is to sort the array in decreasing order and return the second largest element in the array.

  1. Sort the array in decreasing order.
  2. We can create a function to sort the elements using a sorting algorithm such as quicksort or use inbuilt sorting functions.
  3. Traverse from index 1(0-based indexing) because the element at index 0 will clearly be the first largest and check whether duplicates of the larger elements exist or not. Finally, return the second element which is not equal to the largest element from the sorted array.
  4. If no such element is found, return -1.
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