quickperm全排列算法分析解释

Question

这个算法用来生成N个元素的可重复全排列。

算法官网：http://www.quickperm.org/

算法描述：

The Counting QuickPerm Algorithm:

   let a[] represent an arbitrary list of objects to permute
   let N equal the length of a[]
   create an integer array p[] of size N to control the iteration       
   initialize p[0] to 0, p[1] to 0, p[2] to 0, ..., and p[N-1] to 0
   initialize index variable i to 1
   while (i < N) do {
      if (p[i] < i) then {
         if i is odd, then let j = p[i] otherwise let j = 0
         swap(a[j], a[i])
         increment p[i] by 1
         let i = 1 (reset i to 1)
      } // end if
      else { // (p[i] equals i)
         let p[i] = 0 (reset p[i] to 0)
         increment i by 1
      } // end else (p[i] equals i)
   } // end while (i < N)