# 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.

## Analysis

Use Hash Table - O(M) space, O(N) time, where M is length of `J`, and N is length of `S`

## Solution

Hash Set - O (N) - (15ms 26.72%)

```java
class Solution {
public int numJewelsInStones(String J, String S) {
if (J == null || J.length() == 0 || S == null || S.length() == 0) {
return 0;
}
HashSet<Character> jewels = new HashSet<Character>();
int count = 0;
for (int i = 0; i < J.length(); i++) {
jewels.add(J.charAt(i));
}
for (int i = 0; i < S.length(); i++) {
if (jewels.contains(S.charAt(i))) {
count++;
}
}
return count;
}
}
```

```java
class Solution {
public int numJewelsInStones(String J, String S) {
HashSet set = new HashSet();

for (int i = 0; i < J.length(); i++) {
set.add(J.substring(i,i+1));
}

int tick = 0;

for (int i = 0; i < S.length(); i++) {
String temp = S.substring(i,i+1);
if (set.contains(temp)) {
tick++;
}
}

return tick;
}
}
```

For small input, this might be better solution

```java
public static int numJewelsInStones(String J, String S) {
int res=0;
for(char c : S.toCharArray()){
if(J.indexOf(c) != -1){
res++;
}
}
return res;
}
```