Senior Software Engineer

You have been given an integer array/list (ARR) of size N. You have to return an array/list PRODUCT such that PRODUCT[i] is equal to the product of all the elements of ARR except ARR[i]

 Note :

Each product can cross the integer limits, so we should take modulo of the operation. 

Take MOD = 10^9 + 7 to always stay in the limits.

Follow up :

Can you try solving the problem in O(1) space?

You are given an array of size ‘N’. The elements of the array are in the range from 1 to ‘N’.

Ideally, the array should contain elements from 1 to ‘N’. But due to some miscalculations, there is a number R in the range [1, N] which appears in the array twice and another number M in the range [1, N] which is missing from the array.

Your task is to find the missing number (M) and the repeating number (R).

For example:

Consider an array of size six. The elements of the array are { 6, 4, 3, 5, 5, 1 }. 
The array should contain elements from one to six. Here, 2 is not present and 5 is occurring twice. Thus, 2 is the missing number (M) and 5 is the repeating number (R). 

Follow Up

Can you do this in linear time and constant additional space?