数组 – 最常见的数组元素

我需要在数组中找到最常见的(模态)元素.

我能想到的最简单的方法是为每个唯一元素设置变量,并为每个元素分配一个计数变量,每次在一个贯穿数组的for循环中记录它时都会增加.

不幸的是,数组的大小是未知的并且将非常大,因此这种方法是无用的.

我在Objective-C中遇到了一个类似的问题,它使用NSCountedSet方法对数组元素进行排名.不幸的是,我对编程非常陌生,只能将第一行翻译成Swift.

建议的方法如下：

var yourArray: NSArray! // My swift translation

    NSCountedSet *set = [[NSCountedSet alloc] initWithArray:yourArray];

    NSMutableDictionary *dict=[NSMutableDictionary new];

    for (id obj in set) {
        [dict setObject:[NSNumber numberWithInteger:[set countForObject:obj]]
            forKey:obj]; //key is date
    }

    NSLog(@"Dict : %@",dict);

    NSMutableArray *top3=[[NSMutableArray alloc]initWithCapacity:3];

    //which dict obj is = max
    if (dict.count>=3) {

        while (top3.count<3) {
            NSInteger max = [[[dict allValues] valueForKeyPath:@"@max.intValue"] intValue];

            for (id obj in set) {
                if (max == [dict[obj] integerValue]) {
                    NSLog(@"--> %@",obj);
                    [top3 addObject:obj];
                    [dict removeObjectForKey:obj];
                }
            }
        }
    }

    NSLog(@"top 3 = %@",top3);

在我的程序中,我需要在数组中找到前五个地名.

@H_404_14@

let a = [1,1,2,3,7,4,6,2] var frequency: [Int:Int] = [:] for x in a { // set frequency to the current count of this element + 1 frequency[x] = (frequency[x] ?? 0) + 1 } let descending = sorted(frequency) { $0.1 > $1.1 }

func frequencies <S: SequenceType where S.Generator.Element: Hashable> (source: S) -> [(S.Generator.Element,Int)] { var frequency: [S.Generator.Element:Int] = [:] for x in source { frequency[x] = (frequency[x] ?? 0) + 1 } return sorted(frequency) { $0.1 > $1.1 } } frequencies(a)

extension SequenceType where Generator.Element: Hashable { func frequencies() -> [(Generator.Element,Int)] { var frequency: [Generator.Element:Int] = [:] for x in self { frequency[x] = (frequency[x] ?? 0) + 1 } return frequency.sort { $0.1 > $1.1 } } } a.frequencies()

extension Sequence where Self.Iterator.Element: Hashable { func frequencies() -> [(Self.Iterator.Element,Int)] { var frequency: [Self.Iterator.Element:Int] = [:] for x in self { frequency[x] = (frequency[x] ?? 0) + 1 } return frequency.sorted { $0.1 > $1.1 } } }

数组 – 最常见的数组元素

猜你在找的Swift相关文章