Question

You're given strings J representing the types of stones that are jewels, and Srepresenting 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.

Difficulty:Easy

Category:Hash-Table

Analyze

Solution

class Solution {
 public:
  int numJewelsInStones(string J, string S) {
    int ans = 0;
    unordered_map<char, int> rec;
    for (char c : J) rec.insert({c, 1});
    for (char c : S) {
      if (rec[c] == 1) ans++;
    }
    return ans;
  }
};