【容斥原理】Arrange the Numbers LightOJ – 1095
Consider this sequence {1, 2, 3 ... N}, as an initial sequence of first N natural numbers. You can rearrange this sequence in many ways. There will be a total of N! arrangements. You have to calculate the number of arrangement of first N natural numbers, where in first M positions; exactly K numbers are in their initial position.
For Example, N = 5, M = 3, K = 2
You should count this arrangement {1, 4, 3, 2, 5},