Objective-c: Inverse of string reverse

The way in which strings are reversed in OC can be handled in two ways:

The first one: remove each character from the string from beginning to end, then add it from the tail to the variable string, and then output it.

The second is to convert a string inside the OC to a string in the C language, then dynamically assign an array, and then copy the contents of the string into the array for the end-to-end exchange operation. Total array length/2 operations.

Mode one: OC version

 
 
 1 -(NSMutableString*)Reverse
 2 {
 3     NSUInteger length = [self length];
 4     NSMutableArray *array = [NSMutableArray arrayWithCapacity:length];
 5     
 6     for(long i=length-1; i>=0; i--)
 7     {
 8         unichar c = [self characterAtIndex:i];
 9         [array addObject:[NSString stringWithFormat:@"%c",c]];
10     }
11     
12     
13     NSMutableString *str = [NSMutableString stringWithCapacity:length];
14     for(int i=0; i<=length-1; i++)
15     {
16         [str appendString:array[i]];
17     }
18     return str;
19  }@end

Mode two: C language version

 
1 @implementation NSString (Reverse)
  2 -(NSMutableString*)Reverse
  3 {
  4 const char *str = [self UTF8String];
  5 NSUInteger length = [self length];
  6 char *pReverse = (char*)malloc(length+1);//Dynamic allocation of space
  7 strcpy(pReverse, str);
  8 for(int i=0; i<length/2; i++)
  9     {
10 char c = pReverse[i];
11 pReverse[i] = pReverse[length-i-1];
12 pReverse[length-i-1] = c;
13}
14 NSMutableString *pstr = [NSMutableString stringWithUTF8String:pReverse];
15 free(pReverse);
16 return pstr;
17}
18 @end

Main function test:

1 // main.m
  2 // Reverse of string
  3 //
  4 // Created by ma c on 15/8/18.
  5 // Copyright (c) 2015 bjsxt. All rights reserved.
  6 //
  7
  8 #import <Foundation/Foundation.h>
  9 #import "NSString+Reverse.h"
10 int main(int argc, const char * argv[])
11 {
12 @autoreleasepool
13 {
14 NSMutableString *string = [NSMutableString stringWithFormat:@"XYQ-CHINA"];
15 NSString *str = [NSString stringWithString:[string Reverse]];
16 NSLog(@"%@",str);
17}
18 return 0;
19} 

The test results are as follows:

2015-08-18 19:42:56.696 Reversal of string [2222:136571] ANIHC-QYX
Program ended with exit code: 0 

Objective-c: Inverse of string reverse