SDE - Intern

You are given an array ‘sum’ which is the prefix sum of an array of coins ‘C’ where ‘C[i]’ is ‘1’ if the coin is real, or ‘0’ if the coin is fake. There is exactly one fake coin in the array.

Return the index of the fake coin. Assume the array to be 0-indexed.

For Example:

‘sum’ = {1,1,2,3} 
Index of the fake coin is 1. 
For the given ‘sum’, ‘C’ will be {1, 0, 1, 1}. Thus the index of the fake coin is 1.

You are given an array of integers ‘coins’ denoting the denomination of coins and another array of integers ‘freq’ denoting the number of coins of each denomination.

You have to find the number of ways to make the sum ‘V’ by selecting some(or all) coins from the array.

The answer can be very large. So, return the answer modulo 1000000007.

For Example :

‘N’ = 3, ‘coins’ = {1, 2, 3}, ‘freq’ = {1, 1, 3}, ‘V’ = 6

For the given example, we can make six by using the following coins:
{1, 2, 3}
{3. 3}
Hence, the answer is 2.

What is Race Condition?
About Semaphores also