1.霍尔法

#include <iostream>
using namespace std;
int partition(int *arr,int left,int right){int pivotIndex=left;while(left<right){while(left<right && arr[right]>=arr[pivotIndex]){right--;}while(left<right && arr[left]<=arr[pivotIndex]){left++;}swap(arr[left],arr[right]);}swap(arr[left],arr[pivotIndex]);return left;
}
void quicksort(int *arr,int left,int right){if(left<right){int pivotIndex=partition(arr,left,right);quicksort(arr,left,pivotIndex-1);quicksort(arr,pivotIndex+1,right);}
}
int main(){int n;cin>>n;int arr[100005];for(int i=0;i<n;i++){cin>>arr[i];}quicksort(arr,0,n-1);for(int i=0;i<n;i++){cout<<arr[i]<<" ";}return 0;
} 

2. 竞赛用

题目链接：https://www.luogu.com.cn/problem/P1177

#include <iostream>
using namespace std;
void quicksort(int *arr,int left,int right){if(left>=right) return;int l=left-1,r=right+1,pivot=arr[(left+right)/2];while(l<r){do l++;while(arr[l]<pivot);do r--;while(arr[r]>pivot);if(l<r) swap(arr[l],arr[r]);}quicksort(arr,left,r);quicksort(arr,r+1,right);
}int main(){int n;cin>>n;int arr[100005];for(int i=0;i<n;i++){cin>>arr[i];}quicksort(arr,0,n-1);for(int i=0;i<n;i++){cout<<arr[i]<<" ";}return 0;
}