LetCode in Swift (771-Jewels and Stones)

文章目录

1. 1. 文档更新说明
2. 2. 前言
3. 3. 771. Jewels and Stones
   1. 3.1. Example1
   2. 3.2. Example2
   3. 3.3. Note
   4. 3.4. Solution

文档更新说明

• 最后更新 2018年03月07日
• 首次更新 2018年03月07日

前言

　　使用Swift语言完成LetCode题目,简单题.

771. Jewels and Stones

You’re given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels.

The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so “a” is considered a different type of stone from “A”.

Example1

Input: J = "aA", S = "aAAbbbb"
Output: 3    

Example2

Input: J = "z", S = "ZZ"
Output: 0   

Note

• S and J will consist of letters and have length at most 50.
• The characters in J are distinct.

Solution

class Solution {
    func numJewelsInStones(_ J: String, _ S: String) -> Int {
        //创建一个字典, 把石头宝石的类型作为key
        var allStoneDic: [Character : Int] = [Character : Int]()
        //得到S字符串中各种类型的石头宝石的数量
        for c in S {
            if let num = allStoneDic[c] {
                allStoneDic[c] = num + 1
            }else {
                allStoneDic[c] = 1
            }
        }
        //使用J里面所有宝石类型作为key,去访问字典
        var jewelsAmount = 0
        for c in J {
            if let num = allStoneDic[c] {
                jewelsAmount += num
            }
        }
        //得到对应宝石的数量
        return jewelsAmount
    }
}