排序之快速排序
快速排序的在内排中起到比较重要的作用，平均时间复杂度达到O(nlogn)。
升序快速排序
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 }
指定排序顺序快速排序
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 }
指定任意对象和排序规则的快速排序
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 }
迭代器类型快速排序
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 }
测试
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 }
