数据结构与算法9---快速排序

快速排序

1. 原理

单轴快排

改进->

双轴快排：Java： arry.sort(int)   经典

算法性能：平均 O（nlogn ）， 最差 （每次选的边界为最大值，每次只能分出一个值， 可优化：随机取值，判断是不是顺序增长/减小）O（n^2）  最小：（nlogn ）

 

1.2 基本实现：

#include<iostream>
#include<ctime>
#include<algorithm>
#include<string.h>
#include<vector>
using namespace std;

class InsertSort{
public:    
    InsertSort(){};
    ~InsertSort(){};
    
int QuickSort(vector<int>&arr , int left, int rightbound){ //效率低，待分析
    if(left>=rightbound) return 0;
    int mid = partition(arr, left, rightbound);
    QuickSort(arr, left, mid-1);//边界不应参加后续排序
    QuickSort(arr, mid+1, rightbound);
  //  print(arr); 
    return 0;
};
int partition1(vector<int>&arr , int leftbound , int rightbound){
    int left  =leftbound;
    int right =rightbound-1;
    int pivot =arr[rightbound];
    while(left<=right){
      while((arr[left]<=pivot)&&(left<=right)){left++;}  
      while((arr[right]>pivot)&&(right>=left)){right--;} 
     
       //   cout<<arr[left]<<" inline " <<arr[right] <<endl;
          swap(arr[left],arr[right]);
        //  print(arr);

    }
   // cout<<arr[left]<<" " <<pivot <<endl;
   if(left<right)
    swap(arr[left],arr[rightbound]);
   // print(arr); 
    return left;
}  

int partition(vector<int>&arr , int leftbound , int rightbound){  //效率高，待分析
    int left  =leftbound;
    int right =rightbound-1;
    int pivot =arr[rightbound];
    while(1){
      while((arr[left]<pivot)&&(left<=right)){left++;}  
      while((arr[right]>pivot)&&(right>=left)){right--;} 
      if(left<right){
       //   cout<<arr[left]<<" inline " <<arr[right] <<endl;
          swap(arr[left],arr[right]);
        //  print(arr);
          left++;
          right--;
      }else{
    //    cout<<"out left= "<<left<<" right="<< right<<endl;
        break;          
      } 
    }
   // cout<<arr[left]<<" " <<pivot <<endl;
    swap(arr[left],arr[rightbound]);
   // print(arr); 
    return left;
}  
    
    
    
int sort(vector<int>&arr){
    //gap =1 is InsertSort
    int gap = 1;//arr.size()>>1;
    for(; gap>0; gap=gap>>1){
        for(int i=gap; i<arr.size(); i++){
            for(int j=i; j>gap-1; j-=gap){
                if(arr[j]<arr[j-gap]){
                    swap(arr[j],arr[j-gap]);
                }else{
                    break;
                }
            }
        }
    }
    return 0;
};

int MergeSort(vector<int>& arr, int left ,int right){
    if(left == right) return 0;

    
    int mid =(right-left)/2 + left;  //括号内不能补+1 否则一直除不尽
   // cout<<"left ="<<left<<" right="<<right<<" mid1="<<mid<<endl;
    MergeSort(arr, left , mid); //left sort
    MergeSort(arr, mid+1 , right); //right sort
    merge(arr,  left ,  mid , right);  //merge 
    
}    
   

void merge(vector<int> &arr, int left , int mid1 ,int right){
  // cout<<"left ="<<left<<" right="<<right<<" mid1="<<mid1<<endl;
    int mid = mid1;
    int i =left;
    int j =mid+1;
    int k =0;
    vector<int> temp(right-left+1);
    while((i<=mid)&&(j<=right)){
        temp[k++] = arr[i]<=arr[j]? arr[i++]:arr[j++];
   //     cout<<"k-1 " << k-1<<"  "<<temp[k-1]<<endl;
    }
    while(i<=mid){ temp[k++]= arr[i++];}
    while(j<=right){ temp[k++]= arr[j++];}
  //  print(temp);
  //  print(arr);  
    for(i=0; i<temp.size(); ++i){  //temp.size()小心越界
        arr[i+left]=temp[i];///left
    }
 //   print(arr);    
}

int K_sort(vector<int>&arr){
    //gap =1 is InsertSort
    int h=1 ;
    while(h<arr.size()/3){ h = 3*h+1;}
    int gap = h;
   // cout<< gap<<endl;
    for(; gap>0; gap=(gap-1)/3){
        for(int i=gap; i<arr.size(); i++){
            for(int j=i; j>gap-1; j-=gap){
                if(arr[j]<arr[j-gap]){
                    swap(arr[j],arr[j-gap]);
                }else{
                    break;
                }
            }
        }
    }
    return 0;
};


void mov(vector<int> &arr,int index ,int end){
    int tmp = arr[end];
    for(int i=end; i>index; --i){
        arr[i]=arr[i-1];
    }
    arr[index]= tmp;
}
void GenRandArr(vector<int> &arr)
{
    srand(time(0));
    for(int i=0; i<arr.size(); ++i){
        arr[i]=rand()%10;
    }
};

void print(const vector<int> &arr)
{
    for(int i=0; i<arr.size(); ++i){
        cout<< arr[i]<<" ";
    }
     cout<<endl;
} 

void compare(vector<int>& arr1, vector<int>&arr2)   
{

    for(int i=0; i<arr1.size(); ++i)
    {
        if(arr1[i]!=arr2[i]){
          cout<<"compare wrong" <<endl;
          return;
        } 
    }
    cout<<"compare right"<<endl;
};
private:   
   void swap(int &a ,int&b){
       int tmp =a;
       a =b;
       b= tmp;
   };
    
    
};

bool cmp(const int &a ,const int &b){
    return (a<b);
}


#define ARR_SIZE 10000
int main(){
    vector<int> arr1(ARR_SIZE);
   
   // int arr[]={7,3,2,8,1,9,5,4,6,10,6};
    
    vector<int> arr2(ARR_SIZE);
    vector<int> arr3(ARR_SIZE);
    clock_t t;
    long sec;
    InsertSort Ins;
    Ins.GenRandArr(arr1);

  //  memcpy((void*)&arr1[0],(void*)&arr[0], ARR_SIZE*sizeof(int));
   // Ins.print(arr1);
    memcpy((void*)&arr3[0],(void*)&arr1[0], ARR_SIZE*sizeof(int));    
    memcpy((void*)&arr2[0],(void*)&arr1[0], ARR_SIZE*sizeof(int));   
    //Ins.print(arr2);
    

    t =clock();
    Ins.K_sort(arr3);
    sec = (clock()-t);
    cout<<"shell Ksort time =" <<sec<<" clock"<<endl;
    
    t =clock();
    sort(arr2.begin(), arr2.end() ,cmp);
     sec = (clock()-t);
    cout<<"SortLib time ="<< sec<<" clock"<<endl;
    t =clock();
  //  Ins.sort(arr1);
   // Ins.MergeSort( arr1, 0 ,arr1.size()-1);
    Ins.QuickSort(arr1, 0, arr1.size()-1);
    sec = (clock()-t);
    cout<<"shell sort time =" <<sec<<" clock"<<endl;





  //  Ins.print(arr1);
  //  Ins.print(arr2);
    Ins.compare(arr1,arr2);
    
}