基本的排序算法（冒泡、快排、插入、选择、归并）

本文链接：https://blog.youkuaiyun.com/maniac_ran/article/details/106398117

1、冒泡排序

#include<iostream>
using namespace std;

const int N = 10000;

int main()
{
	int n;
	int num[N];
	cout << "请你输入你要排序数的个数：";
	cin >> n;

	for (int i = 0; i < n; i++)
		cin >> num[i];

	//冒泡排序的核心就是逐个比较、交换
	for(int i=0;i<n-1;i++)
		for (int j = 0; j < n - 1; j++)
		{
			if (num[j] > num[j + 1])//如果左边比右边大则交换
			{
				int t = num[j];
				num[j] = num[j + 1];
				num[j + 1] = t;
			}
		}

	for (int i = 0; i < n; i++)
		cout << num[i] << " ";
	system("pause");
	return 0;
}

java写法

package javastudy01;

import java.util.Scanner;

/**
 * @author shkstart
 * @create 2022-03-11 11:59
 * 冒泡排序
 * 双重循环，每重循环只和相邻元素比较大小。
 */
public class Test01 {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
//        int a = sc.nextInt();
        int[] arr = new int[6];
        //输入
        for(int i = 0; i < 6; i++) arr[i] = sc.nextInt();
        //冒泡排序
        for(int i = 0; i < 5; i++){
            for(int j = 0; j < 5; j++){
                if(arr[i] < arr[j])
                {
                    int temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
            }
        }
        //输出
        for(int i = 0; i < 6; i++) System.out.print(arr[i] + " ");
//        System.out.println(a);
    }
}

2、快速排序

快速排序是排序算法中时间复杂度为O（log(n)）的算法。快排的写法有很多，建议大家多写写，看那种方式自己更能接受

#include<iostream>
#include<algorithm>
using namespace std;

const int N = 10000;
int num[N];   //全局数组

void sort_quick(int left,int right)
{
	if (left >= right) return;

	int i = left - 1, j = right + 1;
	int x = num[(i + j) / 2];

	while (i < j)
	{
		do i++; while (num[i] < x);
		do j--; while (num[j] > x);
		if (i < j) swap(num[i], num[j]);
	}

	sort_quick(left, j);
	sort_quick(j + 1, right);   
}
int main()
{
	int n;
	cout << "请你输入你要排序数的个数：";
	cin >> n;
	for (int i = 0; i < n; i++) cin >> num[i];

	sort_quick(0, n - 1);

	for (int i = 0; i < n; i++) cout << num[i] << " ";
	system("pause");
	return 0;
}

java写法

package javastudy01;

import java.util.Scanner;

/**
 * @author shkstart
 * @create 2022-03-11 11:59
 * 快速排序
 * 双指针算法
 */
public class Test01 {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
//        int a = sc.nextInt();
        int[] arr = new int[6];
        //输入
        for(int i = 0; i < 6; i++) arr[i] = sc.nextInt();
        //快速排序
        quicksort(arr, 0, arr.length - 1);
        //输出
        for(int i = 0; i < 6; i++) System.out.print(arr[i] + " ");
//        System.out.println(a);
    }

    /**
     * 快速排序
     * @param arr
     * @param l
     * @param r
     * @return
     */
    public static void quicksort(int[] arr,int l, int r){

        if(l >= r) return;
        int mid = (l + r) / 2;
        int i = l, j = r;

        while(i < j){
            while(arr[i] <= arr[mid] && i < mid) i++;
            while(arr[j] >= arr[mid] && j > mid) j--;

            if(i < j){
                int temp;
                temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
            }
        }
        //递归处理左边和右边
        quicksort(arr, l, mid);
        quicksort(arr, mid + 1, r);
    }
}

3、插入排序

#include<iostream>
using namespace std;

const int N = 10000;
int num[N];
int n;

void insertsort()
{
	for (int i = 1; i < n; i++)
	{
		int t = num[i], j = i;//t临时存放num[i]
		//从i开始往前扫描，如果t比num[j]小，num[j]=num[j-1],j--;
		while (t < num[j - 1] && j - 1 >= 0)
		{
			num[j] = num[j - 1];
			j--;
		}
		num[j] = t;
	}
}
int main()
{
	cout << "请你输入你要排序数的个数：";
	cin >> n;
	for (int i = 0; i < n; i++) cin >> num[i];

	insertsort();

	for (int i = 0; i < n; i++)  cout << num[i] << " ";
	system("pause");
	return 0;
}

4、选择排序

#include<iostream>
using namespace std;

const int N = 10000;
int num[N];
int n;

void selectsort()
{
	for (int i = 0; i < n; i++)
	{
		int t = i;
		for (int j = i; j < n; j++)
		{
			if (num[t] > num[j]) t = j;
		}
		int temp = num[t];
		num[t] = num[i];
		num[i] = temp;
	}
}
int main()
{
	cout << "请你输入你要排序数的个数：";
	cin >> n;
	for (int i = 0; i < n; i++) cin >> num[i];

	selectsort();

	for (int i = 0; i < n; i++)  cout << num[i] << " ";
	system("pause");
	return 0;
}

5、归并排序

版本一

#include<iostream>
using namespace std;

const int N = 10000;
int num[N];
int n;

void merge(int l1, int r1, int l2, int r2)
{
	int q[N], i, j, index = 0;
	i = l1, j = l2;
	while (i <= r1 && j <= r2)
	{
		if (num[i] < num[j]) q[index++] = num[i++];
		else q[index++] = num[j++];
	}
	//左右序列剩余的放入q数组
	while (i <= r1) q[index++] = num[i++];
	while (j <= r2) q[index++] = num[j++];
	//将q临时存储的数值放回num数组中
	for (int k = 0; k < index; k++)
		num[l1 + k] = q[k];
}
void mergesort(int left, int right)
{
	int mid = (left + right) / 2;
	if (left < right)
	{
		mergesort(left, mid);
		mergesort(mid + 1, right);
		merge(left, mid, mid + 1, right);//把左右两边合并
	}
}
int main()
{
	cout << "请你输入你要排序数的个数：";
	cin >> n;
	for (int i = 0; i < n; i++) cin >> num[i];

	mergesort(0, n - 1);

	for (int i = 0; i < n; i++)  cout << num[i] << " ";
	system("pause");
	return 0;
}

版本二

#include<iostream>
#include<cstdio>
using namespace std;

const int N = 1000010;
int a[N], tem[N];
int n;

void merge_sort(int l, int r)
{
    if(l >= r) return;
    
    int mid = (l + r) / 2;
    merge_sort(l, mid), merge_sort(mid + 1, r);
    
    int k = 0, i = l, j = mid + 1;
    while(i <= mid && j <= r)
        if(a[i] < a[j]) tem[k++] = a[i++];
        else tem[k++] = a[j++];
    
    while(i <= mid) tem[k++] = a[i++];
    while(j <= r) tem[k++] = a[j++];
    
    for(int i = l, j = 0; i <= r; i++, j++) a[i] = tem[j];
}
int main()
{
    scanf("%d", &n);
    
    for(int i = 0; i < n; i++) scanf("%d", &a[i]);
    
    merge_sort(0, n - 1);
    
    for(int i = 0; i < n; i++) printf("%d ", a[i]);
    
    return 0;
}