从一个数组中查找另一个数组中的 NSString（for 循环和 isEqualToString 问题）

Question

我想添加 NSArray *small 中的对象，只要它们不存在于 NSArray *big 中。 但输出显示*big 中存在的*small 中的对象已被添加。我已经尝试过 x isEqualToString: x == NO （我知道它与 range.location 和 hasPrefix 不同，但奇怪的是，即使 hiya -> 当它确实存在于 *big 中时也会添加） 和range.location = NSNotFound和x hasPrefix：x == NO。但它们都不起作用。为什么？

顺便说一下，*small 包含的对象比 *big 少。有关系吗？

下面的代码：

NSArray *big = [[NSArray alloc] initWithObjects:@"hello ->hi", @"hiya ->", @"hiya ->whatever", @"hiya -> howdy", @"good day ->hello", @"nope, but ->no", @"however ->what", @"May ->april", @"mai ->", nil];
NSArray *small = [[NSArray alloc] initWithObjects: @"match", @"hiya ->",@"hiya ->", @"hiya ->",@"nope, but ->", @"however ->", @"May ->", nil];


NSString *same;

NSMutableArray *newWords = [[NSMutableArray alloc]init];
newWords = [NSMutableArray  arrayWithArray: big];

NSLog (@"big: %@", big);


int i;
for (i = 0; i<[small count]; i++)

{
    same = [small objectAtIndex:i];
    for (NSString *s in big)
    {
        //NSRange ran = [s rangeOfString:same];
        //if (ran.location =NSNotFound)
        //if ([s isEqualToString: same] == NO)

        if ([s hasPrefix:same] == NO)

        {
            [newWords addObject:same];
            break;
        }
    }
}

输出显示：

2011-10-17 19:21:56.855 scanner2[4018:207] newWords: (
    "hello ->hi",
    "hiya ->",
    "hiya ->whatever",
    "hiya -> howdy",
    "good day ->hello",
    "nope, but ->no",
    "however ->what",
    "May ->april",
    "mai ->",
    match,
    "hiya ->",
    "hiya ->",
    "hiya ->",
    "nope, but ->",
    "however ->",
    "May ->"
)

---

编辑：我什至尝试了 if ([x Compare: x ] !=NSOrderedSame)，但只添加了三次 hiya -> *新词。

Answer 1

您正在将 Small 中的每个字符串与 Big 中的每个字符串进行比较。如果 Big 中的任何字符串与您要比较的字符串不同，则将其添加到 Big 中。但实际上，如果所有字符串都不相同，您需要添加它。所以，你需要等到检查完整个大数组之后。

试试这个：

for (NSString *same in small) {
    BOOL found = NO;
    for (NSString *s in big) {
        if ([s hasPrefix:same] == YES) {
            found = YES;
            break;
        }
    }
    if (!found) {
       [newWords addObject:same];
    }
}

为了迂腐，我应该补充一点，如果数组比您显示的演示字符串大得多，那么您可能需要将 Big 维护为排序数组，以便您可以找到存在或不存在快得多。

例如：

NSArray *big = [[NSArray alloc] initWithObjects:@"hello ->hi", @"hiya ->", @"hiya ->whatever", @"hiya -> howdy", @"good day ->hello", @"nope, but ->no", @"however ->what", @"May ->april", @"mai ->", nil];
NSArray *small = [[NSArray alloc] initWithObjects: @"match", @"hiya ->",@"hiya ->", @"hiya ->",@"nope, but ->", @"however ->", @"May ->", @"match",nil];

NSDate *start = [NSDate date];

NSMutableArray *newWords = [NSMutableArray  arrayWithArray: big];

for (NSString *same in small) {
    BOOL found = NO;
    for (NSString *s in big) {
        if ([s isEqualToString:same] == YES) {
            found = YES;
            break;
        }
    }
    if (!found) {
        [newWords addObject:same];
    }
}

NSLog(@"Time for original method: %fms ",-[start timeIntervalSinceNow]*1000);

start = [NSDate date];
/*
 static NSStringCompareOptions comparisonOptions = NSCaseInsensitiveSearch;
 NSLocale *currentLocale = [NSLocale currentLocale];
 NSComparator sort = ^(id string1, id string2) {
 NSRange string1Range = NSMakeRange(0, [string1 length]);
 return [string1 compare:string2 options:comparisonOptions range:string1Range locale:currentLocale];
 };*/

NSComparator sort = ^(id s1, id s2) { return [s1 compare:s2]; };

newWords = [NSMutableArray arrayWithArray: 
            [big sortedArrayUsingComparator:sort]]; 

for (NSString *same in small) {
    NSUInteger i = [newWords indexOfObject:same 
                             inSortedRange:NSMakeRange(0, [newWords count]) 
                                   options:NSBinarySearchingInsertionIndex 
                           usingComparator:sort ];
    if (![same isEqualToString:[newWords objectAtIndex:i]] ) {
        [newWords insertObject:same atIndex:i];
    }
}
//    }
NSLog(@"Time for new method: %fms ",-[start timeIntervalSinceNow]*1000);
[big release];
[small release];

显然，如果您多次执行此操作，只需将大小保持为已排序的可变数组，而不是每次都重新排序。

Answer 2

你的逻辑很糟糕。您应该结束整个循环来添加元素，您添加得太早了。您需要检查 big 中的每个人都没有这个前缀（不是其中一些）。