# LeetCode 771

Using a hash map or a hash table is very prominent in the world of authentication, encryption, cryptography and much more! Hash tables help us encrypt information or data using key-value pairs.

In this article, it will be a brief overview of how to solve LeetCode 771.

The question is,

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"`

.

My steps include:

- Create a new hash
- Initialize a counter equal to 0
- Set the hash with elements in the Jewels string.
- Iterate over the Stones string and determine if current iteration is in the Hash. If it is, increment a counter
- Return the counter

var numJewelsInStones = function(jewels, stones) {

//step 1

let hash = new Map()

//step 2

let count = 0

//step 3

for (let ele of jewels) {

hash.set(ele, ele)

}

//step 4

for (let i=0; i < stones.length; i++) {

if (hash.get(stones[i])) {

count++

}

}

//step 5

return count

}; let count = 0

for (let ele of jewels) {

hash.set(ele, ele)

}

for (let i=0; i < stones.length; i++) {

if (hash.get(stones[i])) {

count++

}

}

return count

};