001package algs22; 002import stdlib.*; 003import java.security.SecureRandom; 004/* *********************************************************************** 005 * Compilation: javac SecureShuffle.java 006 * Execution: java SecureShuffle < list.txt 007 * 008 * Reads in a list of strings and prints them in random order. 009 * Our shuffling algorithm guarantees to rearrange the elements 010 * in uniformly random order, under the assumption that Math.random() 011 * generates independent and uniformly distributed numbers between 012 * 0 and 1. 013 * 014 * % more cards.txt 015 * 2C 3C 4C 5C 6C 7C 8C 9C 10C JC QC KC AC 016 * 2D 3D 4D 5D 6D 7D 8D 9D 10D JD QD KD AD 017 * 2H 3H 4H 5H 6H 7H 8H 9H 10H JH QH KH AH 018 * 2S 3S 4S 5S 6S 7S 8S 9S 10S JS QS KS AS 019 * 020 * % java Shuffle < cards.txt 021 * 6H 022 * 9C 023 * 8H 024 * 7C 025 * JS 026 * ... 027 * KH 028 * 029 *************************************************************************/ 030 031public class XSecureShuffle { 032 public static void main(String[] args) { 033 034 // read in the data 035 String[] a = StdIn.readAll().split("\\s+"); 036 int N = a.length; 037 038 // create random array of real numbers between 0 and 1 039 SecureRandom random = new SecureRandom(); 040 Double[] r = new Double[N]; 041 for (int i = 0; i < N; i++) { 042 r[i] = random.nextDouble(); 043 } 044 045 // shuffle and get resulting permutation 046 int[] index = Merge.indexSort(r); 047 048 // print permutation 049 for (int i = 0; i < N; i++) 050 StdOut.println(a[index[i]]); 051 } 052}