大二算法复习

快速排序

c++

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N=1e5+10;
int n,a[N];
void quicksort(int l,int r)
{
    if(l>=r)return;
    int mid=(l+r)/2;
    int x=a[mid];
    int i=l-1,j=r+1;
    while(i<j){
        do i++;while(a[i]<x);
        do j--;while(a[j]>x);
        if(i<j)swap(a[i],a[j]);
    }
    quicksort(l,j);
    quicksort(j+1,r);
}

int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
    cin>>a[i];
    quicksort(1,n);
    for(int i=1;i<=n;i++)
    cout<<a[i]<<' ';
    
    
}

java

import java.util.*;
public class quicksort {
    static Scanner sc = new Scanner(System.in);
    static int n = sc.nextInt();
    static int[] q = new int[n];
    public static void main(String[] args) {

        for (int i = 0; i < n; i++) {
            q[i] = sc.nextInt();
        }
        QuickSort(0, n - 1);
        for (int i = 0; i < n; i++) {
            System.out.print(q[i] + " ");
        }
    }
    public static void QuickSort(int l,int r){
        if(l>=r)return;
        int x=q[l+r>>1],i=l-1,j=r+1;
        while(i<j){
            do i++;while(q[i]<x);
            do j--;while(q[j]>x);
            if(i<j){
                int t=q[i];
                q[i]=q[j];
                q[j]=t;
            }
        }
        QuickSort(l,j);
        QuickSort(j+1,r);
        System.out.println();
    }
}