三刷215

Author: diguage

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

@@ -36,15 +36,35 @@ image::images/0215-01.gif[{image_attr}]
 image::images/0215-02.png[{image_attr}]
 
 [[src-0215]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0215_KthLargestElementInAnArray.java[tag=answer]
 ----
+--
 
+二刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0215_KthLargestElementInAnArray_2.java[tag=answer]
 ----
+--
+
+三刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0215_KthLargestElementInAnArray_3.java[tag=answer]
+----
+--
+====
 
 == 参考资料
 

logbook/202406.adoc

@@ -808,6 +808,11 @@
 |{doc_base_url}/0415-add-strings.adoc[题解]
 |✅ 双指针，从后向前，模拟加法进位。
 
+|{counter:codes}
+|{leetcode_base_url}/kth-largest-element-in-an-array/[215. Kth Largest Element in an Array^]
+|{doc_base_url}/0215-kth-largest-element-in-an-array.adoc[题解]
+|❌ 快速查找，知道思路，代码却无从下手。
+
 |===
 
 截止目前，本轮练习一共完成 {codes} 道题。

src/main/java/com/diguage/algo/leetcode/_0215_KthLargestElementInAnArray_3.java

@@ -0,0 +1,40 @@
+package com.diguage.algo.leetcode;
+
+public class _0215_KthLargestElementInAnArray_3 {
+  // tag::answer[]
+
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2024-09-20 23:27:08
+   */
+  public int findKthLargest(int[] nums, int k) {
+    // 第 k 大，即为第 n - k 小
+    return quickselect(nums, nums.length - k, 0, nums.length - 1);
+  }
+
+  private int quickselect(int[] nums, int k, int left, int right) {
+    if (left == right) {
+      return nums[k];
+    }
+    int pivot = nums[left], l = left - 1, r = right + 1;
+    while (l < r) {
+      do {
+        l++;
+      } while (nums[l] < pivot);
+      do {
+        r--;
+      } while (nums[r] > pivot);
+      if (l < r) {
+        int tmp = nums[l];
+        nums[l] = nums[r];
+        nums[r] = tmp;
+      }
+    }
+    if (k <= r) {
+      return quickselect(nums, k, left, r);
+    } else {
+      return quickselect(nums, k, r + 1, right);
+    }
+  }
+  // end::answer[]
+}