Frequency Counts
March 8, 2019
Today we have a tricky exercise from Geeks For Geeks:
Given an unsorted array of n integers from 1 to n, possibly with some items appearing multiple times and others missing from the array, count the frequency of all items that are present. Your solution must run in O(n) time and take O(1) extra space.
Your task is to write a program to count frequencies as described above. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.
Programming Praxis 