# Leetcode 771. Jewels and Stones

Today we are going to solve Leetcode 771. Jewels and Stones

**Problem Statement**

You’re given strings `jewels`

representing the types of stones that are jewels, and `stones`

representing the stones you have. Each character in `stones`

is a type of stone you have. You want to know how many of the stones you have are also jewels.

Letters are case sensitive, so `"a"`

is considered a different type of stone from `"A"`

.

**Example 1:**

**Input:** jewels = "aA", stones = "aAAbbbb"

**Output:** 3

**Example 2:**

**Input:** jewels = "z", stones = "ZZ"

**Output:** 0

**Constraints:**

`1 <= jewels.length, stones.length <= 50`

`jewels`

and`stones`

consist of only English letters.- All the characters of
`jewels`

are**unique**.

# Solution

As we can see from the problem statement, this is a problem for finding the occurrence of one character in another string. Here we are asked to find the number of stones that are jewels. We are given the Jewels and Stones. Therefore, what we can do is that we can add the jewels in an `HashSet`

and count the number of stones that are also jewels. We are using `HashSet`

because with `HashSet`

, we can find an entry in `O(1)`

time. The code can be found below.

Time Complexity: O(n), n is the length of the stones string

Space Complexity: O(m), m is the length of the jewels string

The code can be found in this repository.