例如，我有一个数组：
let dates = ["01/02/16", "02/02/16", "03/02/16", "01/02/16", "02/02/16"]
我喜欢做的是将字典中的每个＜code＞String＜/code＞日期存储为关键字，对于每个重复的关键字，我喜欢将其索引存储为数组，并将其与重复的关键字相关联。
例如，01/02/16 出现在索引 0 和 3 处。02/02/16 发生在索引 1 和 4 处。
我喜欢有一本这样的字典:
[ "01/02/16": [0, 3], "02/02/16": [2, 4], "03/02/16": [1] ]
我知道如何跟踪有多少重复条目，如下所示：
let dates = ["01/02/16", "01/02/16", "02/02/16", "03/02/16"]
var dateCounts:[String:Int] = [:]
for date in dates
{
dateCounts[date] = (dateCounts[date] ?? 0) + 1
}
for (key, value) in dateCounts
{
print("\(key) occurs \(value) time/s")
}
但是，我不确定如何跟踪重复的索引？
试试这个
import UIKit
class ViewController: UIViewController {
var duplicatedDict : [String:[Int]] = [:]
let dates = ["01/02/16", "01/02/16", "02/02/16", "03/02/16"]
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
for (index,dateString) in dates.enumerated() {
if(duplicatedDict[dateString] == nil){
duplicatedDict[dateString] = [index]
}else{
duplicatedDict[dateString]?.append(index)
}
}
debugPrint(duplicatedDict)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
控制台日志输出
["02/02/16": [2], "01/02/16": [0, 1], "03/02/16": [3]]
希望这有帮助
