如何在swift中查找字符串数组中出现的字母

Question

我是初学者，尝试实现这个逻辑，谁能建议这个逻辑?

func findLetterOccurence(Letter: String){
let array = ["Data", "program", "questions", "Helpful"]
///Logic to find the given letter occurences in string array
print("(Letter) occured in (count) times")
}

预期输出:a出现在3次

我试过了:

var count = 0
for i in array {
var newArray.append(i)
count = components(separatedBy: newArray).count - 1
}

但是我不明白组件内部的逻辑到底是什么(separatedBy:) ?我的意思是，如果没有更高的函数，我们怎么能在这里实现逻辑呢?

Answer 1

有几种方法

@discardableResult func findLetterOccurence(letter: String) -> Int {

let array = ["Data", "program", "questions", "Helpful"]
var count = 0
// here we join the array into a single string. Then for each character we check if the lowercased version matches the string lowercased value. 
array.joined().forEach({ if $0.lowercased() == letter.lowercased() { count += 1} } )

print("(letter) occured in (count) times")

return count
}

你也可以做一个敏感的比较，而不使用大小写说

array.joined().forEach({ if String($0) == letter { count += 1} } )

另一种方式是

//here our argument is a character because maybe we just want to search for a single letter.
@discardableResult func findLetterOccurence2(character: Character) -> Int {

let array = ["Data", "program", "questions", "Helpful"]

//again join the array into a single string. and reduce takes the `into` parameter and passes it into the closure as $0 in this case, and each element of the string gets passed in the second argument of the closure.
let count = array.joined().reduce(into: 0) {
$0 += $1.lowercased() == letter.lowercased() ? 1 : 0
}
print("(letter) occured in (count) times")

return count
}

Answer 2

试试这样:

func findLetterOccurence(letter: String) {
var count = 0
for word in array { count += word.filter{ String($0) == letter}.count }
print("--> (letter) occured in (count) times")
}

如果你想要不区分大小写，你必须调整，像这样:

func findLetterOccurence(letter: String) {
var count = 0
for word in array { count += word.filter{ String($0).lowercased() == letter.lowercased()}.count }
print("--> (letter) occured in (count) times")
}

Answer 3

添加此扩展以查找字符串

中出现的later

extension String {
func numberOfOccurrencesOf(string: String) -> Int {
return self.components(separatedBy:string).count - 1
}
}

用于数组

func findLetterOccurence(Letter: String){
let array = ["Data", "program", "questions", "Helpful"]
var number = 0
for str in array{
var l = Letter
//            uncomment it to use code for upper case and lower case both
//            l = str.lowercased()

number = number + str.numberOfOccurrencesOf(string: l)
}
print("(Letter) occured in (number) times")
}