//
// ViewController.m
// arrayfundemo
//
// Created by tql on 2019/12/30.
// Copyright © 2019 tqlLW. All rights reserved.
//

import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];

NSMutableArray *muarray = [NSMutableArray array];

for (int i = 0; i<20; i++) {
    [muarray addObject:[NSString stringWithFormat:@"%d",i]];
}

NSLog(@"%@",muarray);


for (int i = 0; i<muarray.count; i++) {
    NSString *item = muarray[i];
    
    if (item.intValue%4==0&&i>0) {
        [muarray removeObjectAtIndex:i];
        i--;
    }
    
}
NSLog(@"====\n%@",muarray);



for (int  i  = 0; i<muarray.count; i++) {
    if (i%4==0&&i>0) {

// [muarray addObject:[NSString stringWithFormat:@"%d",i+1]];
[muarray insertObject:[NSString stringWithFormat:@"%d",i] atIndex:i+1];
}
i++;
}
NSLog(@"====\n%@",muarray);

}

@end

//console

2019-12-31 10:38:18.449872+0800 arrayfundemo[26077:1307573] (
0,
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19
)
2019-12-31 10:38:18.450031+0800 arrayfundemo[26077:1307573] ====
(
0,
1,
2,
3,
5,
6,
7,
9,
10,
11,
13,
14,
15,
17,
18,
19
)
2019-12-31 10:38:18.450138+0800 arrayfundemo[26077:1307573] ====
(
0,
1,
2,
3,
5,
4,
6,
7,
9,
8,
10,
11,
13,
12,
14,
15,
17,
16,
18,
19
)