Day2. JewelsAndStones.cpp

/*
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".

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.
   
   Hide Hint #1  
For each stone, check if it is a jewel.

*/

class Solution {
public:
    int numJewelsInStones(string J, string S) {
        set<char> st;
        char c;
        for(int i=0;i<J.size();i++){
            c=J[i];                     //store every Jewel in set.
            st.insert(c);
        }
        
        int count=0;                   //For counting number of jewels present in stone.
        for(int i=0;i<S.size();i++){
            c=S[i];
            if(st.find(c)!=st.end())   //if stone at ith index is present in set increase the count
                count++;
        }
        return count;                  //after traversing all stones return count i.e number of jewels present in stone.
    }
};