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| 1 | +# Find Second Largest Element |
| 2 | + |
| 3 | +#### Problem statement |
| 4 | + |
| 5 | +Given an unsorted array, write a function to find the second largest element in the array. |
| 6 | + |
| 7 | +#### Approach |
| 8 | + |
| 9 | +- Find the largest element in the array by traversing through the array using a loop and store the value in a variable (for ex: a ) |
| 10 | +- Assign a variable to store the negative infinite value, which stores the least value (for ex: b ) |
| 11 | +- Run a loop from zero to the size of the array. |
| 12 | +- Now check whether the current element is greater than variable "b" and also not equal to variable "a", which is the largest number in the array. |
| 13 | +- if the above condition is true, then the variable b stores the current element. |
| 14 | + |
| 15 | +#### Time Complexity |
| 16 | + |
| 17 | +- Best case: `O(n)` |
| 18 | +- Average case: `O(n)` |
| 19 | +- Worst case: `O(n)` |
| 20 | + |
| 21 | +#### Space Complexity |
| 22 | + |
| 23 | +Worst case: `O(1)` |
| 24 | + |
| 25 | +#### Example |
| 26 | + |
| 27 | +```txt |
| 28 | +arr = [2, 5, 3, 9, 12, 34, 25] |
| 29 | +Indexes: 0 1 2 3 4 5 6 |
| 30 | +a = max(arr) |
| 31 | +(a = 34) |
| 32 | +b = float("-inf") |
| 33 | + |
| 34 | +Traverse elements from i = 0 to i = 6 |
| 35 | +i = 0 |
| 36 | +Check if b < arr[i] (arr[0]) and arr[0] != a |
| 37 | +True : b = arr[0] (b = 2) |
| 38 | + |
| 39 | +i = 1 |
| 40 | +Check if b < arr[i] (arr[1]) and arr[1] != a |
| 41 | +True : b = arr[0] (b = 5) |
| 42 | + |
| 43 | +i = 2 |
| 44 | +Check if b < arr[i] (arr[2]) and arr[2] != a |
| 45 | +False : As b = 5 is greater than the current element arr[2] = 3 |
| 46 | +continues with the loop |
| 47 | + |
| 48 | +i = 3 |
| 49 | +Check if b < arr[i] (arr[3]) and arr[3] != a |
| 50 | +True : b = arr[3] (b = 9) |
| 51 | + |
| 52 | +i = 4 |
| 53 | +Check if b < arr[i] (arr[4]) and arr[4] != a |
| 54 | +True : b = arr[4] (b = 12) |
| 55 | + |
| 56 | +i = 5 |
| 57 | +Check if b < arr[i] (arr[5]) and arr[5] != a |
| 58 | +False: As current element is equal to the variable "a" which stores the highest value in the array |
| 59 | +continues with the loop |
| 60 | + |
| 61 | +i = 6 |
| 62 | +Check if b < arr[i] (arr[6]) and arr[6] != a |
| 63 | +True : b = arr[6] (b = 25) |
| 64 | + |
| 65 | +Now we get the value 25 in the variable "b", which is the second highest value in the array. |
| 66 | +``` |
| 67 | + |
| 68 | +#### Code Implementation Links |
| 69 | + |
| 70 | +[JavaScript](https://github.com/TheAlgorithms/JavaScript/blob/master/Sorts/FindSecondLargestElement.js) |
| 71 | + |
| 72 | +#### Video Explanation |
| 73 | + |
| 74 | +[Video explaining 2 approaches](https://www.youtube.com/watch?v=Mv8jhYQEbkA) |
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