arrays - 我将如何快速对数组中的项目进行分类？

Question

在 swift 中，我想对现有数组中的项目进行分类，并将它们相应地放入一个新字符串中。

这是我想做的一个例子:

originalArray = ["hotdog","fries","hotdog","coke","coke","fries","hotdog"]

resultingString = "hotdog x 3, fries x 2, coke x 2"

我该怎么做？

Answer 1

试试这个:

let originalArray = ["hotdog","fries","hotdog","coke","coke","fries","hotdog"]
var dict = [String: Int]()

let resultString = originalArray.reduce(dict) { _, element in
    if dict[element] == nil {
        dict[element] = 1
    } else {
        dict[element]! += 1
    }
    return dict
}
.map { "\($0) x \($1)" }
.joinWithSeparator(", ")

如果想保持数组原来的顺序(即:热狗、薯条、可乐)，代码稍微复杂一点:

let originalArray = ["hotdog","fries","hotdog","coke","coke","fries","hotdog"]
var dict = [String: (index: Int, count: Int)]()

let resultString = originalArray.enumerate()
    .reduce(dict) { _ , e in
        if let value = dict[e.element] {
            dict[e.element] = (index: value.index, count: value.count + 1)
        } else {
            dict[e.element] = (index: e.index, count: 1)
        }
        return dict
    }
    .sort { return $0.1.index < $1.1.index }
    .map { "\($0) x \($1.count)" }
    .joinWithSeparator(", ")

print(resultString)