Leetcode: Jewels and Stones

Jewels and Stones

Similar Problems:

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


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

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

// Blog link: https://code.dennyzhang.com/jewels-and-stones
// Basic Ideas: set/hashmap
// Complexity: Time O(n), Space O(n)
func numJewelsInStones(J string, S string) int {
    m := map[rune]bool{}
    for _, ch := range J {
        m[ch] = true
    res := 0
    for _, ch := range S {
        if m[ch] == true { res++ }
    return res

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