top k frequent solution by the hashmap

Author: leebeanbin

top-k-frequent-elements/leebeanbin.java

@@ -0,0 +1,16 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class Solution {
+	public int[] topKFrequent(int[] nums, int k) {
+		Map<Integer, Integer> map = new HashMap<>();
+
+		// count how many duplicated numbers in the input array
+		for (int num : nums) {
+			map.put(num, map.getOrDefault(num, 0) + 1);
+		}
+
+		return map.entrySet().stream().sorted((a, b) -> b.getValue() - a.getValue()).limit(k)
+				.mapToInt(Map.Entry::getKey).toArray();
+	}
+}