title: An improved qsort() function in c
body: <p>Suppose we are sorting a 1D array using qsort(), is there a simple way to retrieve from an element of the sorted array the index tis very element had when it was indexed in the array before it was sorted. Let's say c[N] become sorted as d[N], how to find from an integer i, j such that c[j]=d[i] ? When I mean a simple way, does qsort (with some additional parameter) stores this kind of information (bijection between indexations before an after sorting) or does it exist a qsort improved function that could sort and retrieve easily this kind of information ?</p>