排序算法

快速排序

#include <iostream>

using namespace std;

const int N =1e6+10;
int n;
int a[N];
void quick_sort(int a[N],int l,int r){
    if(l>=r) return ;
    int x = a[(l+r)>>1],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]);
    }
    quick_sort(a,l,j);
    quick_sort(a,j+1,r);
}

int main (){
    cin >>n;
    for (int i = 0;i<n;i++) scanf("%d",&a[i]);
    quick_sort(a,0,n-1);
    for(int i=0;i<n;i++) cout <<a[i]<<' ';
}

归并排序

#include <iostream>

using namespace std;

const int N = 1e6+10;

int n;
int q[N],tmp[N];
 void merge_sort(int q[N],int l ,int r){
    if(l>=r) return ;
    int mid =l+r>>1;
    merge_sort(q,l,mid); merge_sort(q,mid+1,r);
    int k = 0,i=l,j=mid+1;
    while (i<=mid&&j<=r){
        if(q[i]<q[j]) tmp[k++] = q[i++];
        else tmp[k++] = q[j++];
    }
    while(i<=mid) tmp[k++]=q[i++];
    while(j<=r) tmp[k++] = q[j++];
    for(int i =l,j=0;i<=r;i++,j++) q[i] = tmp[j];
}

int main (){
    cin >>n;
    for(int i=0;i<n;i++) scanf("%d",&q[i]);
    merge_sort(q,0,n-1);
    for(int i=0;i<n;i++) printf("%d ",q[i]);
    return 0;
    
}