top K Frequent

Author: geegong

contains-duplicate/Geegong.java

@@ -0,0 +1,80 @@
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Map;
+
+public class Geegong {
+
+    public int[] topKFrequent(int[] nums, int k) {
+        int[] result = new int[k];
+
+        // key : key / value : count
+        Map<Integer, Integer> keyMap = new HashMap<>();
+
+        // key : count / value : HashSet<Integer> keys
+        Map<Integer, HashSet<Integer>> countMap = new HashMap<>();
+
+        // 가장 많이 출연한 친구
+        int maxCount = 0;
+
+        for (int num : nums) {
+            int countToBePut = 0;
+
+            if (keyMap.containsKey(num)) {
+                Integer alreadyCounted = keyMap.get(num);
+                countToBePut = alreadyCounted + 1;
+                keyMap.put(num, countToBePut);
+
+                checkCountMapAndPutCount(countMap, num, countToBePut);
+            } else {
+                countToBePut = 1;
+                keyMap.put(num, countToBePut);
+                checkCountMapAndPutCount(countMap, num, countToBePut);
+            }
+
+            maxCount = Math.max(maxCount, countToBePut);
+        }
+
+
+        // 가장 큰 숫자부터 꺼내볼까요오오오 우후
+        int kIndex=0;
+        for (int index=maxCount; index >= 0; index--) {
+            if (kIndex >= k) {
+                return result;
+            }
+
+            if (countMap.containsKey(index)) {
+                HashSet<Integer> hashNums = countMap.get(index);
+                Iterator<Integer> iterator = hashNums.iterator();
+                while(iterator.hasNext()) {
+
+                    if (kIndex >= k) {
+                        return result;
+                    }
+
+                    result[kIndex] = iterator.next();
+                    kIndex++;
+                }
+
+            }
+
+        }
+
+        return result;
+
+
+    }
+
+    public void checkCountMapAndPutCount(Map<Integer, HashSet<Integer>> countMap, int key, int count) {
+        if (countMap.containsKey(count)) {
+            HashSet<Integer> already = countMap.get(count);
+            already.add(key);
+        } else {
+            HashSet<Integer> newSet = new HashSet<>();
+            newSet.add(key);
+            countMap.put(count, newSet);
+        }
+
+    }
+
+}