Create the fastest sorting array code in C

Create the fastest sorting array code in C: 1: We have a C array define as bellow: double* CreateDoubleArray(int size) { double* pDoubleArray = malloc( sizeof( double )*size ); return pDoubleArray; } """ 2: A = CreateDoubleArray(N) 3: for i in N: A[i] = a double some values of A could be empty ex: A[28] = empty 4: create a c function to sort A according to the float value. Ex: A = A[1]= 1.02 A[2]= 3.656 A[6]= 0.56 A[8]= 0.01 A[9]= 5.36 A[10]= 62.36 here A[3,4,5,7] are not defined it is normal, should work like this. Could associate a specific value to those cases, ex: -1000. At the end I need to recover a new integer array B of the sorted (descending or ascending inlclude an input to decide) positions: Ex: B=[10,9,2,1,6,8] here. Please pass B as an input of the function return nothing but fill properly B. So function should be: getposition(A(array to order),B (array of positions),1 or -1(ascending or descending)) Should be very fast with array of 5000 numbers. Thanks, Yannick