2024/9/21 LeetCode Hot100 堆

src/main/java/com/cool/hot100/heap/MedianFinder.java

@@ -0,0 +1,52 @@
+package com.cool.hot100.heap;
+
+import org.junit.Test;
+
+import java.util.PriorityQueue;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/21/22:50
+ * DayNumber 2
+ * Hard 3
+ * Level 6
+ */
+public class MedianFinder {
+
+
+    private PriorityQueue<Integer> minQueue;
+    private PriorityQueue<Integer> maxQueue;
+
+    public MedianFinder() {
+        minQueue = new PriorityQueue<Integer>((a, b) -> (b - a));
+        maxQueue = new PriorityQueue<Integer>((a, b) -> (a - b));
+    }
+
+    public void addNum(int num) {
+        if (minQueue.isEmpty() || minQueue.peek() >= num) {
+            minQueue.offer(num);
+            if (minQueue.size() > maxQueue.size() + 1) {
+                maxQueue.offer(minQueue.poll());
+            }
+        } else {
+            maxQueue.offer(num);
+            if (maxQueue.size() > minQueue.size()) {
+                minQueue.offer(maxQueue.poll());
+            }
+        }
+    }
+
+    public double findMedian() {
+        if (minQueue.size() > maxQueue.size()) {
+            return minQueue.peek();
+        }
+        return (minQueue.peek() + maxQueue.peek()) / 2.0;
+    }
+    @Test
+    public void test(){
+        new MedianFinder().findMedian();
+    }
+}
+

src/main/java/com/cool/hot100/heap/Num347.java

@@ -0,0 +1,63 @@
+package com.cool.hot100.heap;
+
+import org.junit.Test;
+
+import java.util.*;
+
+/**
+ * Created with IntelliJ IDEA.
+ *
+ * @Author: Cool
+ * @Date: 2024/09/21/19:27
+ * DayNumber 1
+ * Hard 2
+ * Level 3
+ */
+public class Num347 {
+
+    public int[] topKFrequent(int[] nums, int k) {
+        Map<Integer,Integer> map=new HashMap<>();
+        for(int num:nums){
+            map.put(num,map.getOrDefault(num,0)+1);
+        }
+        Set<Map.Entry<Integer, Integer>> entries = map.entrySet();
+        List<Map.Entry<Integer,Integer>> list=new ArrayList<>(entries);
+        int heapSize=map.size();
+        buildMaxHeap(list, heapSize);
+        int[] res=new int[k];
+        int index=0;
+        for(int i=list.size()-1;i>=list.size()-k;i--){
+            res[index++]=list.get(0).getKey();
+            Collections.swap(list,0,i);
+            buildMaxHeap(list,0,--heapSize);
+        }
+        return res;
+    }
+
+    public void buildMaxHeap(List<Map.Entry<Integer,Integer>> list,int heapSize){
+        for(int i=(heapSize)/2;i>=0;i--){
+            buildMaxHeap(list,i,heapSize);
+        }
+    }
+
+    private void buildMaxHeap(List<Map.Entry<Integer,Integer>> list,int i,int heapSize){
+
+        int left=2*i+1,right=2*i+2,largest=i;
+        if(left<heapSize&&list.get(largest).getValue()<list.get(left).getValue()){
+            largest=left;
+        }
+        if(right<heapSize&&list.get(largest).getValue()<list.get(right).getValue()){
+            largest=right;
+        }
+        if(largest!=i){
+            Collections.swap(list,i,largest);
+            buildMaxHeap(list,largest,heapSize);
+        }
+    }
+
+    @Test
+    public void test(){
+        topKFrequent(new int[]{1,1,1,2,2,3},2);
+    }
+
+}