排序-快速排序

快速排序

//
//  ViewController.m
//  quicksort
//
//  Created by zhangyifan on 2021/9/28.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    NSMutableArray *arr = [NSMutableArray arrayWithObjects:@15,@14,@22,@56,@19,@2,@9,@6,@3,@8,@5,@7,@23,@15,@34, nil];
    [self quicksort:arr start:0 end:arr.count-1];

    NSLog(@"我拍好了 %@ ",arr);
}

- (void)quicksort:(NSMutableArray *)marr start:(NSInteger)s end:(NSInteger)e{
    
    if (s >= e){
        return;
    }
    int k = [marr[s] intValue];
    NSInteger i = s,j = e;
    
    while (i < j) {
        while ((i < j) && ([marr[j] intValue]  >= k)) {
            j--;
        }
        [self swap:marr indexa:i indexb:j];
        while ( (i < j) && ([marr[i] intValue] < k)) {
            i++;
        }
        [self swap:marr indexa:i indexb:j];
    }
    
    [self quicksort:marr start:s end:j];
    [self quicksort:marr start:j+1 end:e];
}

- (void)swap:(NSMutableArray *)m indexa:(NSInteger)a indexb:(NSInteger)b{
    
    NSNumber *n = m[a];
    m[a] = m[b];
    m[b] = n;
}



@end