@implementation NSString (Reverse)
-(NSString *)reverseOfString
{
//定义一个可变字符串
NSMutableString *str = [NSMutableString string];
//按倒序遍历字符串
for(int i=(int)self.length-1; i>=0; i--)
{ //按倒序获取每个字符串的range
NSRange range =NSMakeRange( i,1);
//将每个字符按照它的range截取下来,并保存在不可变字符串s中
NSString *s = [self substringWithRange: range];
//将每个单字符的字符串s拼接到可变字符串str中
[str appendString: s];
}return str;
}
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