洗牌算法

面试问题：如何对10首音乐随机播放？

知识点：洗牌算法。

C++版:

 #include <cstdlib>
 #include <iostream>
 using namespace std;

 int rand(int range_start, int range_end)
 {
     srand((unsigned int)time(NULL));
     return rand()%(range_end - range_start) + range_start;
 }

 void swap(int* a, int* b)
 {
     int* temp;
     *temp = *a;
     *a = *b;
     *b = *temp;
 }
 void shuffle(int a[], int len)
 {
     int shuffle_key;
     for(int i = 0; i< len; i++)
     {
         shuffle_key = rand(0, len);
         swap(a[i], a[shuffle_key]);
     }
 }

 int main(int argc, char *argv[])
 {
     int a[8]={3, 5, 7, 2, 12, 1, 5, 6};
     shuffle(a, 8);
     for(int i = 0; i < 8; i++)
     {
         printf("%d", a[i]);
     }
     system("PAUSE");
     return EXIT_SUCCESS;
 }

Java版:

 import java.util.Random;

 public class agorithm {
     public static void main(String arg[]){
         String[] musicUrl={"/music/1.mp3",
                 "/music/2.mp3",
                 "/music/3.mp3",
                 "/music/4.mp3",
                 "/music/5.mp3",
                 "/music/6.mp3",
                 "/music/7.mp3",
                 "/music/8.mp3",
                 "/music/9.mp3",
                 "/music/10.mp3"};

         shuffle(musicUrl);
         for(String music:musicUrl){
             System.out.println(music);
         }
     }
     public static void shuffle(String[] musicUrl){
         int shuffle_key;
         String temp;
         Random rand = new Random();

         for(int i = 0; i < musicUrl.length; i++){
             shuffle_key = rand.nextInt(musicUrl.length-1);
             temp = musicUrl[i];
             musicUrl[i] = musicUrl[shuffle_key];
             musicUrl[shuffle_key] = temp;
         }
     }
 }