NSArray *temp = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", @"5", @"6", nil];

    NSMutableArray *tempArray = [[NSMutableArray alloc] initWithArray:temp];

    NSMutableArray *resultArray = [[NSMutableArray alloc] init];

    int i;

    int count = temp.count;

    for (i = 0; i < count; i ++) {

        int index = arc4random() % (count - i);

        [resultArray addObject:[tempArray objectAtIndex:index]];

        [tempArray removeObjectAtIndex:index];

    }

    [tempArray release];

    NSLog(@"resultArray is %@",resultArray);

    NSLog(@"看看结果楼");

看不懂在下面留言，我会解释

- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError *)error

{

    [self orderToPlayBackGroundMusic];

}

- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag

{

    [self orderToPlayBackGroundMusic];

}

-(void)orderToPlayBackGroundMusic

{

    [SingleTonTool defaultMemory].musicIndex++;

    if ([SingleTonTool defaultMemory].musicIndex == [[SingleTonTool defaultMemory].musicArray count])

    {

        [SingleTonTool defaultMemory].musicIndex = 0;

    }

    NSString * musicName = [[SingleTonTool defaultMemory].musicArray objectAtIndex:[SingleTonTool defaultMemory].musicIndex];

    NSString * musicFilePath = [[NSBundle mainBundle] pathForResource:musicName ofType:@"mp3"];      //创建音乐文件路径

    NSURL * musicURL= [[NSURL alloc] initFileURLWithPath:musicFilePath];

    AVAudioPlayer * thePlayer  = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL error:nil];

    thePlayer.delegate = self;

    [thePlayer play];

    [thePlayer setVolume:1];   //设置音量大小

    thePlayer.numberOfLoops = 1;//设置音乐播放次数  -1为一直循环

    [musicURL release];

    [SingleTonTool defaultMemory].thePlayer = thePlayer;

    [[SingleTonTool defaultMemory].playerArray removeAllObjects];

    [[SingleTonTool defaultMemory].playerArray addObject:thePlayer];

}

-(void)playBackGroundSound

{

    [SingleTonTool defaultMemory].musicArray = [[NSMutableArray alloc] initWithCapacity:0];

    [[SingleTonTool defaultMemory].musicArray addObject:@"初音ミク-World Is Mine"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"Avril Lavigne-Girlfrieng"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"浜崎あゆみ-evolution"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"植物大战僵尸 通关歌曲"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"初音ミク-炉心融解"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"杜岩-千年缘《仙剑奇侠传四》主题曲"];

    [[SingleTonTool defaultMemory].musicArray addObject:@"初音ミク-深海少女"];

    int k = arc4random()%3;

    switch (k)

    {

        case 0:

            [SingleTonTool defaultMemory].musicIndex = 0;

            break;

        case 1:

            [SingleTonTool defaultMemory].musicIndex = 2;

            break;

        case 2:

            [SingleTonTool defaultMemory].musicIndex = 3;

            break;

        default:

            [SingleTonTool defaultMemory].musicIndex = 3;

            break;

    }

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];

    NSError *err = nil;

    [audioSession setCategory :AVAudioSessionCategoryPlayAndRecord error:&err];

    if(err)

    {

        NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]);

    }

    [audioSession setActive:YES error:&err];

    err = nil;

    if(err)

    {

        NSLog(@"audioSession: %@ %d %@", [err domain], [err code], [[err userInfo] description]);

    }

    //禁止程序运行时自动锁屏

    [[UIApplication sharedApplication] setIdleTimerDisabled:YES];

    NSString * musicFilePath = [[NSBundle mainBundle] pathForResource:[[SingleTonTool defaultMemory].musicArray objectAtIndex:[SingleTonTool defaultMemory].musicIndex] ofType:@"mp3"];      //创建音乐文件路径

   NSURL * musicURL= [[NSURL alloc] initFileURLWithPath:musicFilePath];

    AVAudioPlayer * thePlayer  = [[AVAudioPlayer alloc] initWithContentsOfURL:musicURL error:nil];

    thePlayer.delegate = self;

    [thePlayer play];

    [thePlayer setVolume:1];   //设置音量大小

    thePlayer.numberOfLoops = 1;//设置音乐播放次数  -1为一直循环

    [musicURL release];

    [[SingleTonTool defaultMemory].playerArray addObject:thePlayer];

    [SingleTonTool defaultMemory].thePlayer = thePlayer;

    //播一半的歌曲退出后台后停止

    /*MPMusicPlayerController *musicPlayer = [MPMusicPlayerController iPodMusicPlayer];

     MPMusicPlaybackState playbackState = musicPlayer.playbackState;

     if (playbackState == MPMusicPlaybackStateStopped || playbackState == MPMusicPlaybackStatePaused) {

     [musicPlayer play];

     } else if (playbackState == MPMusicPlaybackStatePlaying) {

     [musicPlayer pause];

     }*/

}

一，指针和数组
         1） C语言中只有一维数组,而且数组的大小必须在编译期就作为一个常数确定下来

         2） 对于一个数组,我们只能够做两件事:确定该数组的大小,以及获得指向该数组下标为0的元素的指针.

#include<stdio.h>
int main()
{
int calendar[12][31];
int (*monthp)[31];
for(monthp = calendar; monthp < &calendar[12]; ++monthp){
   int *dayp;
   for(dayp = *monthp; dayp < &(*monthp)[31]; ++dayp)
       *dayp = 0;
}
}

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main()
{
   char *r;
   char *s = "hi";
   char *t = "man";
   r = malloc(strlen(s)+strlen(t)+1); //包括最后的'/0',strlen不包括'/0'
   if(!r){
       exit(1);
   }
   strcpy(r,s);
   strcat(r,t);
   printf("%s\n",r);
    free(r);
}

#include<stdio.h>

int * bsearch(int *t,int n,int x){
int *lo = t,*hi = t + n-1;
while(lo < hi){
    int *mid = lo + ((hi-lo) >> 1);
    //不能为int *mid = (hi + lo) / 2因为对指针进行加法是错误的，
    //只能对指针进行迭代即++或--，或相减计算距离
    if(x < *mid){
        hi = mid - 1;
    }else if (x > *mid){
            lo = mid + 1;
        }else{
            return mid;
        }
     }
     return NULL;
}
int main()
{
      int a[] = {1,2,3,4};
      printf("%d",*bsearch(a,4,2));
}

任何时候已存放的字符数都是bufptr-buffer