771. Jewels and Stones

题目

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".

Example 1:

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

Example 2:

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.

题目大意

给定字符串 J 代表石头中宝石的类型，和字符串 S 代表你拥有的石头。S 中每个字符代表了一种你拥有的石头的类型，你想知道你拥有的石头中有多少是宝石。

J 中的字母不重复，J 和 S 中的所有字符都是字母。字母区分大小写，因此 "a" 和 "A" 是不同类型的石头。

解题思路

• 给出 2 个字符串，要求在 S 字符串中找出在 J 字符串里面出现的字符个数。这是一道简单题。

代码

package leetcode

import "strings"

// 解法一
func numJewelsInStones(J string, S string) int {
	count := 0
	for i := range S {
		if strings.Contains(J, string(S[i])) {
			count++
		}
	}
	return count
}

// 解法二
func numJewelsInStones1(J string, S string) int {
	cache, result := make(map[rune]bool), 0
	for _, r := range J {
		cache[r] = true
	}
	for _, r := range S {
		if _, ok := cache[r]; ok {
			result++
		}
	}
	return result
}