我的输入（NSString）可以是("text")，{("text")}或(“text”){{“text”}}。在所有这些情况下，我必须确保开始分隔符（{）获得自己的结束分隔符（}）。
例如，{{“text”})应标记为错误。
我正在尝试NSScanner来完成此任务，并且还尝试将字符串反转并比较每个字符以寻找相反的字符，但一直遇到麻烦。
最好的方法是什么？
这是我尝试过的最新方式：
NSMutableString *reversedString = [NSMutableString string];
NSInteger charIndex = [_expressionTextField.text length];
while (charIndex > 0) {
charIndex--;
NSRange subStrRange = NSMakeRange(charIndex, 1);
[reversedString appendString:[_expressionTextField.text substringWithRange:subStrRange]];
}
NSString *mystring = _expressionTextField.text;
NSLog(@"%@", reversedString);
for (int i = 0; i < reversedString.length; i++) {
if ([mystring characterAtIndex:i] == [reversedString characterAtIndex:(reversedString.length -i)]) {
NSLog(@"Closed the bracket");
}
}
答案 0 :(得分：5)
我使用NSScanner对它进行了破解。我认为这对于非常长的琴弦来说比vikingosegundo快一点，因为我只是一次直接穿过一个角色。没有搜索或子串制作。在大多数情况下，它可能不会有所作为。
/// Takes a string and a dictionary of delimiter pairs in which the keys are the
/// opening characters of the pairs and the values the closers. Returns YES if the
/// delimiters in the string are balanced, otherwise NO. Ignores any characters
/// not present in the dictionary.
///
/// Note: Does not support multi-character delimiters.
BOOL stringHasBalancedDelimiters(NSString * s, NSDictionary * delimiterPairs)
{
NSMutableArray * delimiterStack = [NSMutableArray array];
NSString * openers = [[delimiterPairs allKeys] componentsJoinedByString:@""];
NSString * closers = [[delimiterPairs allValues] componentsJoinedByString:@""];
NSCharacterSet * openerSet = [NSCharacterSet characterSetWithCharactersInString:openers];
NSCharacterSet * closerSet = [NSCharacterSet characterSetWithCharactersInString:closers];
NSMutableCharacterSet * delimiterSet = [openerSet mutableCopy];
[delimiterSet formUnionWithCharacterSet:closerSet];
NSScanner * scanner = [NSScanner scannerWithString:s];
while( ![scanner isAtEnd] ){
// Move up to the next delimiter of either kind
[scanner scanUpToCharactersFromSet:delimiterSet intoString:nil];
NSString * delimiter;
// Could be a closer.
if( [scanner WSSScanSingleCharacterFromSet:closerSet intoString:&delimiter] ){
// Got a paired closer; pop the opener off the stack and continue.
NSString * expected = [delimiterStack lastObject];
if( [expected isEqualToString:delimiter] ){
[delimiterStack removeLastObject];
continue;
}
// Not the right closer, but if the members of the pair are
// identical, treat as an opener.
else if( [delimiterPairs[delimiter] isEqualToString:delimiter] ){
[delimiterStack addObject:delimiterPairs[delimiter]];
continue;
}
// Otherwise this is a failure.
else {
return NO;
}
}
// Otherwise it's an opener (or nothing, thus the if).
if( [scanner WSSScanSingleCharacterFromSet:openerSet intoString:&delimiter] ){
[delimiterStack addObject:delimiterPairs[delimiter]];
}
}
// Haven't failed and nothing left to pair? Success.
return [delimiterStack count] == 0;
}
我为NSScanner添加了一种方法，让我的生活更轻松。这样我们就不必扫描一堆字符（因为分隔符可以彼此相邻），然后将它们拆分成单独的NSString。
@interface NSScanner (WSSSingleCharacter)
- (BOOL)WSSScanSingleCharacterFromSet:(NSCharacterSet *)charSet intoString:(NSString * __autoreleasing *)string;
@end
@implementation NSScanner (WSSSingleCharacter)
- (BOOL)WSSScanSingleCharacterFromSet:(NSCharacterSet *)charSet intoString:(NSString *__autoreleasing *)string
{
if( [self isAtEnd] ) return NO;
NSUInteger loc = [self scanLocation];
unichar character = [[self string] characterAtIndex:loc];
if( [charSet characterIsMember:character] ){
if( string ){
*string = [NSString stringWithCharacters:&character length:1];
}
[self setScanLocation:loc+1];
return YES;
}
else {
return NO;
}
}
@end
一些测试：
NSDictionary * delimiterPairs = @{@"{" : @"}",
@"[" : @"]",
@"\"" : @"\"",
@"'" : @"'",
@"(" : @")"};
// Balanced simple nesting
NSString * s = @"{(\"text\")}";
// Balanced complex nesting
NSString * t = @"{({}'(text)[\"\"]')text}";
// Balanced symmetrical delimiters at beginning and end of string, as
// well as after both an opener and closer from a different pair
NSString * u = @"\"\"(\"text\"\"\")\"\"";
// Out of order
NSString * v = @"{(\"text)\"}";
// Unpaired at the beginning
NSString * w = @"\"{text}";
// Unpaired at the end
NSString * x = @"\"'text'\"(";
// Unpaired in the middle
NSString * y = @"[(text)']";
for( NSString * string in @[s, t, u, v, w, x, y] ){
BOOL paired = stringHasBalancedDelimiters(string, delimiterPairs);
NSLog(@"%d", paired);
}
答案 1 :(得分：0)
您必须跟踪最新的分隔符符号并出现。
你可以给我们一个堆栈：通过每个找到的开口分隔符。当您找到正确的结账时，请删除最后一个。
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSMutableArray *stack = [NSMutableArray array];
NSString *text = @"(“text”){{“text”}}}";
NSArray *delimiterPairs = @[@[@"(", @")"],@[@"{", @"}"]];
NSMutableString *openingDelimiters = [@"" mutableCopy];
NSMutableString *closingDelimiters = [@"" mutableCopy];
[delimiterPairs enumerateObjectsUsingBlock:^(NSArray *pair, NSUInteger idx, BOOL *stop) {
[openingDelimiters appendString:pair[0]];
[closingDelimiters appendString:pair[1]];
}];
NSScanner *scanner = [NSScanner scannerWithString:text];
__block BOOL unbalanced = NO;
while (![scanner isAtEnd] && !unbalanced) {
[scanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:[openingDelimiters stringByAppendingString:closingDelimiters]]
intoString:NULL];
NSString *currentDelimiter = [text substringWithRange:NSMakeRange([scanner scanLocation], 1)];
if ([openingDelimiters rangeOfString:currentDelimiter].location != NSNotFound) {
[stack addObject:currentDelimiter];
} else {
[delimiterPairs enumerateObjectsUsingBlock:^(NSArray *pair, NSUInteger idx, BOOL *stop) {
if([currentDelimiter isEqualToString:pair[1]]){
if([stack count] == 0) {
unbalanced = YES;
} else if ([[stack lastObject] isEqualToString:pair[0]]) {
[stack removeLastObject];
}
*stop = YES;
}
}];
}
scanner.scanLocation +=1;
}
if ([stack count])
unbalanced = YES;
}
return 0;
}
如果分隔符不匹配，则bool不平衡将为YES;