给你一个整数数组 nums,将该数组升序排列。
示例 1:
输入:nums = [5,2,3,1]输出:[1,2,3,5]
示例 2:
输入:nums = [5,1,1,2,0,0]输出:[0,0,1,1,2,5]
提示:
1 <= nums.length <= 50000
-50000 <= nums[i] <= 50000
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/sort-an-array
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这道题没有什么好说的,快排就完事了;
引申:Arrays中的sort(DualPivotQuicksort 即双轴快排)源码值得一看,sort是一个综合了快排,归并,直接选择,插入排序等的多因素排序方法,
源码的设计者应该是根据大量数据计算出的几个数据量边界,以此来决定使用最优的排序算法;
sort源码的部分片段:
/** * This class implements the Dual-Pivot Quicksort algorithm by * Vladimir Yaroslavskiy, Jon Bentley, and Josh Bloch. The algorithm * offers O(n log(n)) performance on many data sets that cause other * quicksorts to degrade to quadratic performance, and is typically * faster than traditional (one-pivot) Quicksort implementations. * 该排序算法是一个双轴快速排序,是三位大神(Vladimir Yaroslavskiy,Jon Bentley, and JoshuaBloch)实现的, * 在大量数据集中,其他快排算法的排序性能最坏时为O(n²),但该算法将一直提供稳定的O(nlogn)排序性能,其效率要优于传统单轴快速排序 * * All exposed methods are package-private, designed to be invoked * from public methods (in class Arrays) after performing any * necessary array bounds checks and expanding parameters into the * required forms. * 所有的方法都是包私有的,以便于在完成必要的边界检查和参数扩展及格式化后供Arrays调用 * * @author Vladimir Yaroslavskiy * @author Jon Bentley * @author Josh Bloch * * @version 2011.02.11 m765.827.12i:5\7pm * @since 1.7 */final class DualPivotQuicksort {...}
几个边界量:
/** * The maximum number of runs in merge sort. * 合并子列最大数量:待合并的序列的最大数量 */private static final int MAX_RUN_COUNT = 67;/** * The maximum length of run in merge sort. * 合并子列最大长度:待合并的序列的最大长度 */private static final int MAX_RUN_LENGTH = 33;/** * If the length of an array to be sorted is less than this * constant, Quicksort is used in preference to merge sort. * 快速排序阈值:若待排序数组的长度小于该值,则优先使用快速排序而不是归并排序 */private static final int QUICKSORT_THRESHOLD = 286;/** * If the length of an array to be sorted is less than this * constant, insertion sort is used in preference to Quicksort. * 插入排序阈值:若待排序数组的长度小于该值,则优先考虑插入排序而不是快速排序 */private static final int INSERTION_SORT_THRESHOLD = 47;/** * If the length of a byte array to be sorted is greater than this * constant, counting sort is used in preference to insertion sort. * byte数组计数排序阈值:若待排序的byte数组长度大于该值,则优先使用计数排序而不是插入排序 */private static final int COUNTING_SORT_THRESHOLD_FOR_BYTE = 29;/** * If the length of a short or char array to be sorted is greater * than this constant, counting sort is used in preference to Quicksort. * short&char数组计数排序阈值:若待排序的数组是short或char类型的且数组长度大于该值,将优先使用计数排序而不是插入排序 */private static final int COUNTING_SORT_THRESHOLD_FOR_SHORT_OR_CHAR = 3200;
步骤:
寻找一个中间值(一般为第一个数),将小于该值的放左边,大于的放右边;
以上一次的终止位置(不包括该位置)为分界线分两块递归进行1的操作;
终结条件为左右索引相遇;
package leetcode;/** * @author ZhouJie * @date 2020年3月31日 上午12:02:03 * @Description: 912. 排序数组 * */public class LeetCode_0912 {}class Solution_0912 { /** * @author: ZhouJie * @date: 2020年3月31日 上午12:50:01 * @param: @param nums * @param: @return * @return: int[] * @Description: 快速排序 * */ public int[] sortArray(int[] nums) { quickSort(nums, 0, nums.length - 1); return nums; } /** * @author: ZhouJie * @date: 2020年3月31日 上午12:50:04 * @param: @param nums * @param: @param start * @param: @param end * @return: void * @Description: 快排核心 * */ private void quickSort(int[] nums, int start, int end) { if (start >= end) { return; } int midVal = nums[start]; int left = start, right = end; while (left < right) { while (left < right && nums[right] >= midVal) { right--; } nums[left] = nums[right]; while (left < right && nums[left] <= midVal) { left++; } nums[right] = nums[left]; } nums[left] = midVal; quickSort(nums, start, left - 1); quickSort(nums, left + 1, end); }}
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