Algorithm to apply permutation in constant memory space

Question

I saw this question is a programming interview book, here I\'m simplifying the question.

Assume you have an array A of length n, and you ha

Answer 1

Here a clearer version which takes a swapElements function that accepts indices, e.g., std::swap(Item[cycle], Item[P[cycle]])$ Essentially it runs through all elements and follows the cycles if they haven't been visited yet. Instead of the second check !visited[P[cycle]], we could also compare with the first element in the cycle which has been done somewhere else above.

 bool visited[n] = {0};
 for (int i = 0; i < n; i++)   {
     int cycle = i;
     while(! visited[cycle] && ! visited[P[cycle]]) {
         swapElements(cycle,P[cycle]);
         visited[cycle]=true;
         cycle = P[cycle];
     }
 }