快速排序

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    NSMutableArray *arr = @[@"9", @"8", @"2", @"6", @"1"].mutableCopy;
 [self QuickSort:arr StartIndex:0 EndIndex:4];
    NSLog(@"%@", arr);
}

-(void)QuickSort:(NSMutableArray *)list StartIndex:(NSInteger)startIndex EndIndex:(NSInteger)endIndex{
    
    if(startIndex >= endIndex)return;
    
    NSNumber * temp = [list objectAtIndex:startIndex];
    NSInteger tempIndex = startIndex; //临时索引 处理交换位置(即下一个交换的对象的位置)
    
    for(int i = (int)startIndex + 1 ; i <= endIndex ; i++){
        
        NSNumber *t = [list objectAtIndex:i];
        
        if([temp intValue] > [t intValue]){
            
            tempIndex = tempIndex + 1;
            
            [list exchangeObjectAtIndex:tempIndex withObjectAtIndex:i];
            
        }
        
    }
    
    [list exchangeObjectAtIndex:tempIndex withObjectAtIndex:startIndex];
    [self QuickSort:list StartIndex:startIndex EndIndex:tempIndex-1];
    [self QuickSort:list StartIndex:tempIndex+1 EndIndex:endIndex];
   
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


@end