refactor 1394

Author: fishercoder1534

README.md

@@ -8,6 +8,7 @@ _If you like this project, please leave me a star._ ★
 
 |  #  |      Title     |   Solutions   | Video  | Difficulty  | Tag                   
 |-----|----------------|---------------|--------|-------------|-------------
+|1394|[Find Lucky Integer in an Array](https://leetcode.com/problems/find-lucky-integer-in-an-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1394.java) | |Easy|Array|
 |1392|[Longest Happy Prefix](https://leetcode.com/problems/longest-happy-prefix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1392.java) | |Hard|String, Rolling Hash|
 |1390|[Four Divisors](https://leetcode.com/problems/four-divisors/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1390.java) | |Medium|Math|
 |1389|[Create Target Array in the Given Order](https://leetcode.com/problems/create-target-array-in-the-given-order/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1389.java) | |Easy|Array|

src/main/java/com/fishercoder/solutions/_1394.java

@@ -0,0 +1,55 @@
+package com.fishercoder.solutions;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 1394. Find Lucky Integer in an Array
+ *
+ * Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.
+ * Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.
+ *
+ * Example 1:
+ * Input: arr = [2,2,3,4]
+ * Output: 2
+ * Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
+ *
+ * Example 2:
+ * Input: arr = [1,2,2,3,3,3]
+ * Output: 3
+ * Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
+ *
+ * Example 3:
+ * Input: arr = [2,2,2,3,3]
+ * Output: -1
+ * Explanation: There are no lucky numbers in the array.
+ *
+ * Example 4:
+ * Input: arr = [5]
+ * Output: -1
+ *
+ * Example 5:
+ * Input: arr = [7,7,7,7,7,7,7]
+ * Output: 7
+ *
+ * Constraints:
+ * 1 <= arr.length <= 500
+ * 1 <= arr[i] <= 500
+ * */
+public class _1394 {
+    public static class Solution1 {
+        public int findLucky(int[] arr) {
+            int lucky = -1;
+            Map<Integer, Integer> map = new HashMap<>();
+            for (int i = 0; i < arr.length; i++) {
+                map.put(arr[i], map.getOrDefault(arr[i], 0) + 1);
+            }
+            for (int num : map.keySet()) {
+                if (num == map.get(num) && num > lucky) {
+                    lucky = num;
+                }
+            }
+            return lucky;
+        }
+    }
+}

src/test/java/com/fishercoder/_1394Test.java

@@ -0,0 +1,39 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1394;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1394Test {
+
+    private static _1394.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1394.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(2, solution1.findLucky(new int[]{2, 2, 3, 4}));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(3, solution1.findLucky(new int[]{1, 2, 2, 3, 3, 3}));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(-1, solution1.findLucky(new int[]{2, 2, 2, 3, 3}));
+    }
+
+    @Test
+    public void test4() {
+        assertEquals(-1, solution1.findLucky(new int[]{5}));
+    }
+
+
+}