Day 28 — Jewels and Stones

Day 28 — Jewels and Stones

100 Days to Amazon

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Hey Guys, Today is day 28 **of the challenge that I took. Wherein I will be solving every day for 100 days the [programming questions]( that have been asked in previous interviews.**

You have a bonus at the end if you keep reading. You can find out the companies that have asked these questions in real interviews.

All these problems are taken from the following [e-book_]( 🎓_

This is completely free 🆓 if you have an amazon kindle subscription.

This e-book contains 100 coding problems that have been asked in top tech interview questions. It also has a guide to solving all the problems in 200+ ways. **These problems I assure you** has been asked in previous interviews.

You have to decide whether you want to go** unprepared *for a tech interview or go ahead and **quick search for this guide *to solve the 100 problems.

Begin Your ascent to greatness

Day 28 — Jewels and Stones


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".


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

Input: J = "z", S = "ZZ"
Output: 0


class Solution {
        public int numJewelsInStones(String J, String S) {

            Map<Character, Integer> map = new HashMap<Character, Integer>();

            for(int i=0; i < J.length(); i++)

                map.put(J.charAt(i), 1);

            int count =0;
            for(int i=0; i<S.length(); i++)

            return count;


Author: Akshay Ravindran


  1. Create a *Hashmap *to store the Stones. Create a counter that stores the result.
  2. Iterate through the String.
  3. For each character check if the *hashmap *contains that character using *ContainsKey *function.
  4. If it contains, *Increase *the counter.
  5. Else, go to the next character.
  6. Return the counter value at the end of the String. 🔚

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