0771. Jewels and Stones

# 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 #

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
}

Sep 6, 2020