add solution for top-k-frequent-elements

Author: Hyeri1ee

top-k-frequent-elements/Hyeri1ee.java

@@ -0,0 +1,38 @@
+import java.util.*;
+
+class Solution {
+    public int[] topKFrequent(int[] nums, int k) {
+        HashMap<Integer, Integer> maps = new HashMap<>(); //nums[i] 대상, 등장 횟수
+        
+            for(int i =0; i <nums.length; i++){
+                maps.put(nums[i], maps.getOrDefault(nums[i], 0) + 1);
+            }
+        
+
+
+        ArrayList<Integer> list = new ArrayList<>();
+        //maps를 value기준으로 내림차순 정렬후, list에 k개만큼만 key값 추가
+        Map<Integer, Integer> sorts = 
+            maps.entrySet()
+            .stream()
+            .sorted(Map.Entry.<Integer, Integer>comparingByValue().reversed())
+            .limit(k)
+            .collect(Collectors.toMap(
+                Map.Entry::getKey,
+                Map.Entry::getValue,
+                (a, b) -> a,
+                LinkedHashMap::new
+            ));
+
+        for(int t : sorts.keySet()){
+            list.add(t);
+        }
+
+        return list.stream()
+                .mapToInt(Integer::intValue)
+                .toArray();
+
+            //list.stream().mapToInt(Integer::intValue).toArray(); 
+            //Arrays.stream(arr).boxed().toList();
+    }
+}