六刷215

Author: diguage

docs/0215-kth-largest-element-in-an-array.adoc

@@ -1,7 +1,7 @@
 [#0215-kth-largest-element-in-an-array]
 = 215. 数组中的第K个最大元素
 
-https://leetcode.cn/problems/kth-largest-element-in-an-array/[LeetCode - 215. 数组中的第K个最大元素 ^]
+https://leetcode.cn/problems/kth-largest-element-in-an-array/[LeetCode - 215. 数组中的第K个最大元素^]
 
 给定整数数组 `nums` 和整数 `k`，请返回数组中第 *`k`* 个最大的元素。
 
@@ -36,6 +36,8 @@ image::images/0215-01.gif[{image_attr}]
 
 image::images/0215-02.png[{image_attr}]
 
+NOTE: 好久不写，生疏了！
+
 [[src-0215]]
 [tabs]
 ====
@@ -83,12 +85,22 @@ include::{sourcedir}/_0215_KthLargestElementInAnArray_4.java[tag=answer]
 include::{sourcedir}/_0215_KthLargestElementInAnArray_5.java[tag=answer]
 ----
 --
+
+六刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0215_KthLargestElementInAnArray_6.java[tag=answer]
+----
+--
 ====
 
 == 参考资料
 
 . https://en.wikipedia.org/wiki/Quickselect[Quickselect - Wikipedia^]
 . https://leetcode.cn/problems/kth-largest-element-in-an-array/solutions/307351/shu-zu-zhong-de-di-kge-zui-da-yuan-su-by-leetcode-/[215. 数组中的第K个最大元素 - 官方题解^]
 . https://leetcode.cn/problems/kth-largest-element-in-an-array/solutions/2361969/215-shu-zu-zhong-de-di-k-ge-zui-da-yuan-d786p/[215. 数组中的第K个最大元素 - 分治，清晰图解^]
+. https://leetcode.cn/problems/kth-largest-element-in-an-array/solutions/3717020/leetcode-215yi-ti-duo-jie-ji-shu-xuan-ze-664r/[215. 数组中的第K个最大元素 - 计数选择法，快速选择法，堆选择法，多种解法+写法，详细分析^]
 
 

logbook/202503.adoc

@@ -1524,6 +1524,11 @@ endif::[]
 |{doc_base_url}/0347-top-k-frequent-elements.adoc[题解]
 |✅ Top K 问题，优先队列；桶排序；也可以利用快速选择。
 
+|{counter:codes2503}
+|{leetcode_base_url}/kth-largest-element-in-an-array/[215. 数组中的第K个最大元素^]
+|{doc_base_url}/0215-kth-largest-element-in-an-array.adoc[题解]
+|⭕️ 快速选择。有思路，但代码总报错！还需要多练！
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

src/main/java/com/diguage/algo/leetcode/_0215_KthLargestElementInAnArray_6.java

@@ -0,0 +1,87 @@
+package com.diguage.algo.leetcode;
+
+public class _0215_KthLargestElementInAnArray_6 {
+  // tag::answer[]
+
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-30 07:16:18
+   */
+  public int findKthLargest(int[] nums, int k) {
+    return quickselect(nums, 0, nums.length - 1, nums.length - k);
+  }
+
+  private int quickselect(int[] nums, int l, int r, int k) {
+    if (l == r) {
+      return nums[k];
+    }
+    int x = nums[l], i = l - 1, j = r + 1;
+    while (i < j) {
+      do {
+        i++;
+      } while (nums[i] < x);
+      do {
+        j--;
+      } while (x < nums[j]);
+      if (i < j) {
+        int tmp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = tmp;
+      }
+    }
+    if (k <= j) {
+      return quickselect(nums, l, j, k);
+    } else {
+      return quickselect(nums, j + 1, r, k);
+    }
+  }
+//  public int findKthLargest(int[] nums, int k) {
+//    if (nums.length == 1) {
+//      return nums[0];
+//    }
+//    int index = partition(nums, 0, nums.length - 1);
+//    k = nums.length - k;
+//    int low = 0, high = nums.length - 1;
+//    while (index != k) {
+//      if (index < k) {
+//        low = index + 1;
+//      } else {
+//        high = index - 1;
+//      }
+//      index = partition(nums, low, high);
+//    }
+//    return nums[k];
+//  }
+
+//  private int partition(int[] nums, int low, int hight) {
+//    int priovt = nums[low];
+//    int l = low, h = hight + 1;
+//    while (true) {
+//      while (nums[++l] < priovt) {
+//        if (l == hight) {
+//          break;
+//        }
+//      }
+//      while (nums[--h] > priovt) {
+//        if (h == low) {
+//          break;
+//        }
+//      }
+//      if (l >= h) {
+//        break;
+//      }
+//      int temp = nums[l];
+//      nums[l] = nums[h];
+//      nums[h] = temp;
+//    }
+//    nums[low] = nums[h];
+//    nums[h] = priovt;
+//    return h;
+//  }
+
+  // end::answer[]
+  public static void main(String[] args) {
+    new _0215_KthLargestElementInAnArray_6()
+      .findKthLargest(new int[]{3, 2, 1, 5, 6, 4}, 2);
+  }
+}