A derangement of n numbers is a permutation of those numbers in which none of the numbers appears in its original place. For example, the numbers {1,2,3} can be deranged into {2,3,1} and {3,1,2}. We can modify this slightly for n numbers that are not necessarily distinct by saying that no number in the derangement can be in the place that a number of the same value was in in the original ordering. So the numbers {1,1,2,2,3} could be deranged into {2,2,1,3,1}, {2,2,3,1,1}, {2,3,1,1,2}, and {3,2,1,1,2}. Write a program that takes a series of numbers and outputs the number of derangements of nums.
sample input: {0,0,0,0,0,0,0,1,1,1,1,1,1,1,2} sample output: 14
sample input: {0,5,4,2,3,6,6} sample output: 640
now how to solve it??? can anyone give a detailed solution..