Given an array of n integers from 1 to n with one integer repeated twice

Problem - Given an array of n integers from 1 to n with one integer repeated twice This can be done via normal array traversal or hash table to find duplicates. But since we are given that the integers are from 1 to n, then there are better methods available. Approach 1 - Arithmetic sum approach So, the efficient method to solve it calculate the sum of actual input array, and expected sum of the array. [Read More]