Advanced Programming I Lecture Notes

3 April 2007 • Hashing Basics

Generating a random permutation using code like

#! /bin/bash
#
# ranperm256 - write to std-out a random permutation of the 256 integers
#   0..255.  The random permutation is writen as a 16x16 matrix.

awk 'BEGIN {
       for (i = 0; i < 256; i++)
         p[i] = i

       srand()
       for (i = 0; i < 255; i++) {
         j = i + int(rand()*(256 - i))
	 t = p[i]
	 p[i] = p[j]
	 p[j] = t
         }

       for (i = 0; i < 16; i++) {
         for (j = 0; j < 16; j++)
	   printf "%4d", p[i*16 + j]
	 print ""
	 }

       exit
       }
    '

This page last modified on 24 January 2006.