347. Top K Frequent Elements update.

08-Heap-and-Priority-Queue/347-Top-K-Frequent-Elements/src/Solution3.java

@@ -0,0 +1,40 @@
+import java.util.*;
+
+/**
+ * @Auther: lss
+ * @Date: 2019/2/26 19:00
+ * @Description:
+ */
+public class Solution3 {
+
+ public List<Integer> topKFrequent(int[] nums, int k) {
+
+ TreeMap<Integer, Integer> map = new TreeMap<>();
+ for (int num : nums) {
+ if (map.containsKey(num))
+ map.put(num, map.get(num) + 1);
+ else
+ map.put(num, 1);
+ }
+
+ PriorityQueue<Integer> pq = new PriorityQueue<>(new Comparator<Integer>() {
+ @Override
+ public int compare(Integer a, Integer b) {
+ return map.get(a) - map.get(b);
+ }
+ });
+ for (int key : map.keySet()) {
+ if (pq.size() < k)
+ pq.add(key);
+ else if (map.get(key) > map.get(pq.peek())) {
+ pq.remove();
+ pq.add(key);
+ }
+ }
+
+ LinkedList<Integer> res = new LinkedList<>();
+ while (!pq.isEmpty())
+ res.add(pq.remove());
+ return res;
+ }
+}

08-Heap-and-Priority-Queue/347-Top-K-Frequent-Elements/src/Solution4.java

@@ -0,0 +1,35 @@
+import java.util.*;
+
+/**
+ * @Auther: lss
+ * @Date: 2019/2/26 19:00
+ * @Description:
+ */
+public class Solution4 {
+
+ public List<Integer> topKFrequent(int[] nums, int k) {
+
+ TreeMap<Integer, Integer> map = new TreeMap<>();
+ for (int num : nums) {
+ if (map.containsKey(num))
+ map.put(num, map.get(num) + 1);
+ else
+ map.put(num, 1);
+ }
+
+ PriorityQueue<Integer> pq = new PriorityQueue<>((a, b) -> map.get(a) - map.get(b));
+ for (int key : map.keySet()) {
+ if (pq.size() < k)
+ pq.add(key);
+ else if (map.get(key) > map.get(pq.peek())) {
+ pq.remove();
+ pq.add(key);
+ }
+ }
+
+ LinkedList<Integer> res = new LinkedList<>();
+ while (!pq.isEmpty())
+ res.add(pq.remove());
+ return res;
+ }
+}