Discover the MEX of given Array

You’re given an array arr[] of dimension N, the duty is to find out the MEX of the array.

MEX is the smallest complete quantity that’s not current within the array.

Examples:

Enter: arr[] = {1, 0, 2, 4}
Output: 3
Clarification: 3 is the smallest complete quantity that’s not current within the array

Enter: arr[] = {-1, -5, 0, 4}
Output: 1
Clarification: 1 is the smallest complete quantity that’s lacking within the array.

Method: Observe the beneath thought to unravel the issue

Type the array in rising order and discover the primary quantity ranging from 0 which isn’t current within the array.

Observe the steps to unravel the issue:

• Type the array.
• Initialize a variable mex = 0.
• Journey over the array from index 0 to N-1.
• If the ingredient is the same as mex
  • Increment mex by 1 i.e., mex = mex + 1
  • Else proceed the iteration
• Return mex as the ultimate reply.

Beneath is the implementation of the above method:

Time Complexity: O(N * logN)
Auxiliary House: O(1)