Fast sorting for sorting and sorting for sorting

Fast sorting for sorting and sorting for sorting

Quick sorting plays an important role in the internal sorting. The average time complexity reaches O (nlogn ).

Sort in ascending order

 1 int partition(vector<int> &vi,int start,int end){ 2     int key=vi[start]; 3     while(start<end){ 4         while(start<end&&vi[end]>=key) 5             end--; 6         vi[start]=vi[end]; 7         while(start<end&&vi[start]<key) 8             start++; 9         vi[end]=vi[start];10     }11     vi[start]=key;12     return start;13 }14 void quickCore(vector<int> &vi,int start,int end){15     if(start<end){16         int idx =partition(vi,start,end);17         quickCore(vi,start,idx-1);18         quickCore(vi,idx+1,end);19     }20 }21 22 void quickSort(vector<int>&vi){23     quickCore(vi,0,vi.size()-1);  24 }

Specify the sorting order for quick sorting

 1 bool cmp(const int &a,const int &b){ 2     return (b-a>=0)?true:false; 3 } 4 bool rcmp(const int &a,const int &b){ 5     return (b-a>=0)?false:true; 6 } 7 int partition(vector<int> &vi,int start,int end,bool (*cmp)(const int&,const int&)){ 8     int key=vi[start]; 9     while(start<end){10         while(start<end&&cmp(key,vi[end]))11             end--;12         vi[start]=vi[end];13         while(start<end&&!cmp(key,vi[start]))14             start++;15         vi[end]=vi[start];16     }17     vi[start]=key;18     return start;19 }20 void quickCore(vector<int> &vi,int start,int end,bool (*cmp)(const int&,const int&)){21     if(start<end){22         int idx =partition(vi,start,end,cmp);23         quickCore(vi,start,idx-1,cmp);24         quickCore(vi,idx+1,end,cmp);25     }26 }27 28 void quickSort(vector<int>&vi,bool (*cmp)(const int&,const int&)){29     quickCore(vi,0,vi.size()-1,cmp);  30 }

Fast sorting of arbitrary objects and sorting rules

 1 struct component{ 2     int a; 3     int b; 4 }; 5 bool cmp(const component& obj1,const component& obj2){ 6     if(obj2.a>obj1.a) 7         return true; 8     else if(obj2.a<obj1.a) 9         return false;10     else if(obj2.b>=obj1.b)11         return true;12     return false;13 }14 bool rcmp(const component& obj1,const component& obj2){15     if(obj1.a>obj2.a)16         return true;17     else if(obj1.a<obj2.a)18         return false;19     else if(obj1.b>=obj2.b)20         return true;21     return false;22 }23 24 template<class T>25 int partition(vector<T> &vi,size_t start,size_t end,bool (*cmp)(const T&,const T&)){26     T key=vi[start];27     while(start<end){28         while(start<end&&cmp(key,vi[end]))29             end--;30         vi[start]=vi[end];31         while(start<end&&!cmp(key,vi[start]))32             start++;33         vi[end]=vi[start];34     }35     vi[start]=key;36     return start;37 }38 template<class T>39 void quickCore(vector<T> &vi,size_t start,size_t end,bool (*cmp)(const T&,const T&)){40     if(start<end){41         size_t idx =partition(vi,start,end,cmp);42         quickCore(vi,start,idx-1,cmp);43         quickCore(vi,idx+1,end,cmp);44     }45 }46 template<class T>47 void quickSort(vector<T>&vi,bool (*cmp)(const T&,const T&)){48     quickCore(vi,0,vi.size()-1,cmp);  49 }

Fast sorting of iterator types

 1 struct component{ 2     int a; 3     int b; 4 }; 5 bool cmp(const component& obj1,const component& obj2){ 6     if(obj2.a>obj1.a) 7         return true; 8     else if(obj2.a<obj1.a) 9         return false;10     else if(obj2.b>=obj1.b)11         return true;12     return false;13 }14 bool rcmp(const component& obj1,const component& obj2){15     if(obj1.a>obj2.a)16         return true;17     else if(obj1.a<obj2.a)18         return false;19     else if(obj1.b>=obj2.b)20         return true;21     return false;22 }23 bool cmp1(const int &a,const int &b){24     return (b-a>=0)?true:false;25 }26 bool rcmp1(const int &a,const int &b){27     return (b-a>=0)?false:true;28 }29 template<class Iterator, class Comparator>30 Iterator partition(Iterator start,Iterator end,Comparator cmp){31     typedef typename iterator_traits<Iterator>::value_type value_type;32     value_type key=*start;33     while(start!=end-1){34         while(start!=end-1&&cmp(key,*(end-1)))35             end--;36         *start=*(end-1);37         while(start!=end-1&&!cmp(key,*start))38             start++;39         *(end-1)=*start;40     }41     *(end-1)=key;42     return end-1;43 }44 template<class Iterator, class Comparator>45 void quickCore(Iterator start,Iterator end,Comparator cmp){46     if(start !=end){47         Iterator idx =::partition(start,end,cmp);48         quickCore(start,idx,cmp);49         quickCore(idx+1,end,cmp);50     }51 }52 template<class Iterator, class Comparator>53 void quickSort(Iterator start,Iterator end,Comparator cmp){54     quickCore(start,end,cmp);  55 }56 template<class Iterator>57 void quickSort(Iterator start,Iterator end){58     quickCore(start,end,less<typename iterator_traits<Iterator>::value_type>());  59 }

Test

 1 #include <iostream> 2 #include<vector> 3 #include<algorithm> 4 #include<set> 5 using namespace std; 6  7 int main( ) 8 {  9     vector<int> vi{1,7,3,1};10     quickSort(vi.begin(),vi.end());11     sort(vi.begin(),vi.end(),cmp1);12     for(int i=0;i<vi.size();i++)13         cout<<vi[i]<<"  ";14     cout<<endl;15     16     vector<component> obj{17       {1,4},18       {3,6},19       {2,8},20       {2,7},21       {1,1}22     };23     quickSort(obj.begin(),obj.end(),cmp);24     for(int i=0;i<obj.size();i++){25         cout<<obj[i].a<<"  "<<obj[i].b<<endl;26     }27     return 0;28 }