iOS开发 字符串倒序的两种方式

在面试中，经常被问到字符串倒序的面试题，下面提供两种简单的实现：

第一种：

- (NSString*)reverseWordsInString:(NSString*)oldStr{

NSMutableString *newStr = [[NSMutableString alloc] initWithCapacity:oldStr.length];

for (int i = (int)oldStr.length - 1; i >= 0; i --) {

    unichar character = [oldStr characterAtIndex:i];

    [newStr appendFormat:@"%c",character];

}

return newStr;

}

第二种：

- (NSString*)reverseWordsInString:(NSString*)oldStr

{

NSMutableString *newStr = [NSMutableString stringWithCapacity:oldStr.length];

[str enumerateSubstringsInRange:NSMakeRange(0, oldStr.length) options:NSStringEnumerationReverse | NSStringEnumerationByComposedCharacterSequences  usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop){

[newStr appendString:substring];

}];

return newStr;

}