TopK

网易面试挂了，伤心。

一面面试官不是搞技术的，二面面试官搞ios，全程不问JVM，并发的知识，运气真差

而且手撸代码硬伤，没得编译

准备先在IDE敲一遍，在再纸上面写一遍。

 package com.qiuzhao.test;

 import java.util.PriorityQueue;
 import java.util.Queue;

 /**
  * @Auther: Chang
  * @Date: 2018/8/27
  */
 public class topK {
     public static void main(String[] args) {

         int[] a = {489, 500, 111, 100, 2, 7, 3, 8, 66, 888};
         int k = 3;
         // 第一种 推排序
         prioritySort(a, k);
         // 第二种 快速排序
         quickSort(a, k);
     }

     // 堆排序 int[] a = {489, -5, 111, 100, 2, 7, 3, 8, 66, 88};
     private static void prioritySort(int[] a, int k) {
         Queue<Integer> pq = new PriorityQueue<>(k);
         for (int i = 0; i < a.length; i++) {
             int n = pq.size();
             if (n >= k && a[i] > pq.peek()) {
                 pq.poll();
             }
             n = pq.size();
             if (n < k) pq.add(a[i]);
         }
         pq.forEach(x -> System.out.print(x + "  "));
         System.out.println();
     }

     private static void quickSort(int[] a, int k) {

         int left = 0;
         int right = a.length - 1;
         int mid = partition(a, left, right);
         while (mid != k) {
             if (mid > k) {
                 right = mid - 1;
                 mid = partition(a, left, right);
             } else {
                 left = mid + 1;
                 mid = partition(a, left, right);
             }
         }
         for (int i = 0; i < mid; i++) {
             System.out.print(a[i] + "  ");
         }
         System.out.println();
     }

     private static int partition(int[] a, int left, int right) {

         int temp = a[left];
         while (left < right) {
             while (left < right && a[right] <= temp) right--;
             a[left] = a[right];
             while (left < right && a[left] >= temp) left++;
             a[right] = a[left];
         }
         a[left] = temp;
         return left;
     }
 }