经典排序算法实现
冒泡排序
选择排序
插入排序
快速排序
堆排序
希尔排序
归并排序
//java 版本
package com.leej.sort;
public class SortAlgorithm {
//冒泡排序, 稳定, On^2
public static void BubbleSort(int[] nums) {
int n = nums.length;
for (int step = 1; step < n; step++) {
boolean changed = false;
for (int j = 0; j < n - step; j++) {
if (nums[j] > nums[j + 1]) {
swap(nums, j, j + 1);
changed = true;
}
}
if (!changed) return;
}
}
//选择排序, 不稳定 On^2
public static void SelectSort(int[] nums) {
int n = nums.length;
for (int i = 0; i < n - 1; i++) {
int minIndex = i;
for (int j = i + 1; j < n; j++) {
if (nums[minIndex] > nums[j])
minIndex = j;
}
if (minIndex != i) swap(nums, i, minIndex);
}
}
//插入排序, 稳定, On^2
public static void InsertSort(int[] nums) {
int n = nums.length;
for (int i = 1; i < n; i++) {
int tmp = nums[i];
int j;
for (j = i; j > 0; j--) {
if (nums[j - 1] > tmp) {
nums[j] = nums[j-1];
}
else break;
}
nums[j] = tmp;
}
}
//快排, 不稳定, Onlogn, On^2
public static void QuickSort(int[] nums, int left, int right) {
if (left >= right) return;
int pIndex = partition(nums, left, right);
QuickSort(nums, left, pIndex - 1);
QuickSort(nums, pIndex + 1, right);
}
private static int partition(int[] nums, int left, int right) {
if (left >= right) return left;
int pivot = nums[left];
while(left < right) {
while(left < right && nums[right] >= pivot) right--;
nums[left] = nums[right];
while(left < right && nums[left] < pivot) left++;
nums[right] = nums[left];
}
nums[left] = pivot;
return left;
}
//堆排序 不稳定 Onlogn
public static void HeapSort(int[] nums) {
int n = nums.length;
for (int i = n/2 - 1; i >= 0; i--) {
MaxHeapify(nums, i, n - 1);
}
for (int i = n - 1; i > 0; i--) {
swap(nums, 0, i);
MaxHeapify(nums, 0, i - 1);
}
}
private static void MaxHeapify(int[] nums, int start, int end) {
int father = start;
int son = father * 2 + 1;
while(son <= end) {
if (son + 1 <= end && nums[son + 1] > nums[son]) son++;
if (nums[father] >= nums[son]) return;
swap(nums, father, son);
father = son;
son = father * 2 + 1;
}
}
//希尔排序 不稳定 On^1.5
public static void ShellSort(int[] nums) {
int gap = 1, i, j, len = nums.length;
int temp;
while(gap < len / 3) gap = gap * 3 + 1;
for (; gap > 0; gap /= 3) {
for (i = gap; i < len; i++) {
temp = nums[i];
for (j = i - gap; j >= 0 && nums[j] > temp; j -= gap)
nums[j + gap] = nums[j];
nums[j + gap] = temp;
}
}
}
//归并排序 稳定 Onlogn
public static void MergeSort(int[] nums) {
if (nums.length <= 1) return;
int[] result = new int[nums.length];
MergeSortRecursive(nums, result, 0, nums.length - 1);
}
private static void MergeSortRecursive(int[] nums, int[] reg, int start, int end) {
if (start >= end) return;
int len = end - start, mid = (len >> 1) + start;
int start1 = start, end1 = mid;
int start2 = mid + 1, end2 = end;
MergeSortRecursive(nums, reg, start1, end1);
MergeSortRecursive(nums, reg, start2, end2);
int k = start;
while (start1 <= end1 && start2 <= end2)
reg[k++] = nums[start1] < nums[start2] ? nums[start1++] : nums[start2++];
while (start1 <= end1)
reg[k++] = nums[start1++];
while (start2 <= end2)
reg[k++] = nums[start2++];
for (k = start; k <= end; k++)
nums[k] = reg[k];
}
public static void showNums(int[] nums) {
for (int num : nums)
System.out.print(num + " ");
System.out.println();
}
private static void swap(int[] nums, int i, int j) {
int tmp = nums[i]; nums[i] = nums[j]; nums[j] = tmp;
}
public static void main(String[] args) {
int[] nums = new int[] {1,3,2,3,4,2,7,5};
showNums(nums);
//quickSort(nums, 0, nums.length - 1);
//BubbleSort(nums);
//SelectSort(nums);
//InsertSort(nums);
//HeapSort(nums);
//ShellSort(nums);
MergeSort(nums);
showNums(nums);
}
}
