第七章 STL 及其应用
2018-01-02 本文已影响20人
DeepWeaver
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
class Predicate{
private:
int count=0;
public:
bool operator()(int data){
if ( count>=3 ) return false;
else{
bool x=(data<=20 && data%3==0);
count+=x;
// cout<<x<<" "<<count<<endl;
return x;
}
}
};
int main(){
Predicate predicate;
vector<int> vec{2,4,5,6,10,15,3,21,36,72,9,13};
vector<int> result;
result.resize (vec.size());
// auto end=copy_if(vec.begin (),vec.end (),result.begin(),predicate);
int count=0;
auto end=copy_if(vec.begin (),vec.end (),result.begin()
,[&count](int data)->bool{
if ( count>=3 ) return false;
else{
bool x=(data<=20 && data%3==0);
count+=x;return x;
}
}
);
result.erase(end,result.end ());
for_each(result.begin (),result.end (),[](int e){cout<<e<<endl;});
return 0;
}
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#include <iostream>
#include <vector>
#include <map>
#include <functional>
#include <string>
#include <algorithm>
#include <sstream>
using namespace std;
class Student{
private:
string name;
string specialty;//专业
long id;// 学号
double creditPoint; //学分积点
public:
Student(string n,string s,long i,double c)
:name(n),specialty(s),id(i),creditPoint(c){}
void setCreditPoint(double c){creditPoint=c;}
double getCreditPoint()const{return creditPoint;}
string getName()const{return name;}
long getId()const{return id;}
string getSpecialty()const{return specialty;}
friend ostream& operator<<(ostream& out,const Student& s);
};
ostream& operator<<(ostream& out,const Student& s){
cout<<"Name:"<<s.name<<endl;
cout<<" Id:"<<s.id<<endl;
cout<<" Specialty:"<<s.specialty<<endl;
cout<<" CreditPoint:"<<s.creditPoint<<endl;
}
class StudentManage{
public:
enum SortType{BY_NAME,BY_ID,BY_SPECIALTY,BY_CRDITPOINT};
StudentManage()=default;
void addStudent();
void removeStudent();
void setSortType(SortType st);
void findStudent();
int size()const{ return students.size();}
friend ostream& operator<<(ostream& out,const StudentManage& sm);
private:
map<long,int> idmap;
vector<Student> students;
SortType sortType=BY_ID;
};void StudentManage::setSortType (SortType st){
/*if (choice>3 || choice<0) {
cout<<"Illigal!\n";
return ;
}
SortType st=(SortType)choice;
cout<<st<<endl;*/
//function+lambda......666
function<bool(const Student&,const Student&)> f;
switch(st){
case BY_ID: f=[](const Student& s1,const Student& s2)
{return s1.getName()<s2.getName();};break;
case BY_NAME:f=[](const Student& s1,const Student& s2)
{return s1.getId()<s2.getId();};break;
case BY_SPECIALTY:f=[](const Student& s1,const Student& s2)
{return s1.getSpecialty()<s2.getSpecialty();};break;
case BY_CRDITPOINT:f=[](const Student& s1,const Student& s2)
{return s1.getCreditPoint()<s2.getCreditPoint();};break;
}
sort(students.begin(),students.end(),f);
}
void StudentManage::addStudent(){
string n,s;long i;double c;
// cout<<"Please enter the name, speciality, id ,credit point of the student:\n";
cin>>n>>s>>i>>c;
if (idmap.count(i)){
cout<<"This id has existed!\n";
return ;
}
else{
idmap[i]++;
students.push_back(Student(n,s,i,c));
setSortType(sortType);
}
}
void StudentManage::removeStudent(){
cout<<"Please enter the student's id you want to remove:\n";
long x;cin>>x;
if (!idmap.count(x)){
cout<<"There is no such a student!\n";
return ;
}
for(auto i=students.begin();i!=students.end();++i){
if( (*i).getId()==x ) {
idmap.erase(x);
students.erase(i);
cout<<"OK!This student is removed!\n";
return ;
}
}
}
void StudentManage::findStudent(){
cout<<"Please enter a name or an id:\n";
string n;cin>>n;
long i;
if (n[0]<='9' && n[0]>='0'){
stringstream ss;ss<<n;ss>>i;
for_each(students.begin(),students.end(),[i](Student& x){if(x.getId()==i) cout<<x<<endl;});
}
else {
for_each(students.begin(),students.end(),[&n](Student& x){if(x.getName()==n) cout<<x<<endl;});
}
}
ostream& operator<<(ostream& out,const StudentManage& sm){
for(auto& e:sm.students) out<<e<<endl;
return out;
}
int main(){
/* cout<<"Test1:\n";
vector<Student> vec{
{"zhang","Computer",11001,4.2},
{"wang","Computer",11002,3.8},
{"Li","English",12001,4.1},
{"Tang","English",12002,3.9},
{"Qian","Computer",11003,4.0},
{"Song","Geology",10001,4.1}
};
for(auto e: vec)
cout<<e;
*/
cout<<"Test2:\n";
StudentManage sm;
cout<<"Welcome to the Student Management System!\nBut can "
<<"I must say the our teacher has less creativity in teaching...\n"
<<"In two continuous semeters this project always is the hardest task...\n"
<<"I only look foward there will be some intersting task in the 14-15th week.\n\n";
cout<<"sort type(0-name,1-id,2-specialty,3-creditpoint):\n";
int choice;
cin>>choice;
sm.setSortType (static_cast<StudentManage::SortType>(choice));
cout<<"\nPlease enter the student number:\n";
int n;cin>>n;
cout<<"Please enter the name, speciality, id ,credit point of the student:\n";
while(n--) sm.addStudent();
cout<<sm;
int command;
while(1){
cout<<"Please enter command, 1-add,2-find,3-remove,0-exit:\n";
cin>>command;
if (command==0) break;
switch(command){
case 1:sm.addStudent();break;
case 2:sm.findStudent();break;
case 3:sm.removeStudent();break;
}
// cout<<endl<<"Now:\n";
// cout<<sm;
}
cout<<"Syytem is shot down!\n";
return 0;
}
Test2:
Welcome to the Student Management System!
But can I must say the our teacher has less creativity in teaching...
In two continuous semeters this project always is the hardest task...
I only look foward there will be some intersting task in the 14-15th week.
#include<bits/stdc++.h>
using namespace std;
int main(){
map<string,int> count;//save as pair
string word;
int n;cin>>n;
while(n--) {
cin>>word;
++count[word];
}
for(auto e:count){//what inside map ??????
cout<<e.first<<"\t"<<e.second<<"\n";//it's sorted as pair
}
}
看情况
#include<iostream>
#include <map>
#include <string>
using namespace std;
#define all(x) x.begin(),x.end()
#define pb push_back
int product(int num1,int num2){
return num1*num2;
}
double geoMean(const list<int>& nums){
double mult=accumulate(all(nums),1,product);
return pow(mult,1.0/nums.size());
}
int main(){
list<int> data;
data.pb(1);data.pb(2);data.pb(4);
cout<<geoMean(data)<<endl;
}
#include<iostream>
#include <map>
#include <string>
#include <list>
using namespace std;
#define all(x) x.begin(),x.end()
#define pb push_back
int product(int num1,int num2){
return num1*num2;
}
double geoMean(const list<int>& nums){
double mult=accumulate(all(nums),1,product);
return pow(mult,1.0/nums.size());
}
int main(){
list<int> data;
data.pb(1);data.pb(2);data.pb(4);
cout<<geoMean(data)<<endl;
}
#include<iostream>
#include<algorithm>
#include<functional>
using namespace std;
using namespace std::placeholders;
int main(){
auto divd=[](auto x,auto y){return x/y;};
auto dint=bind<int>(divd,_1,_2);
auto rddou=bind(divd,_2,_1);
cout<<dint(20,6)<<endl;
cout<<rddou((double)20,(double)6)<<endl;
}
include<iostream>
using namespace std;
int main(){
enum week{Monday,Tuesday,Wednesday};
week a=Monday;
a=(week)1;
cout<<&a<<endl;
cout<<(int)a<<endl;
cout<<a<<endl;
}
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#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
void myfunction (int i)
{
cout << " " << i;
}
struct myclass
{
void operator() (int i)
{
cout << " " << i;
}
} myobject;
class MeanVlaue
{
public:
MeanVlaue():num(0),sum(0){}
void operator() (int elem)
{
num++;
sum+=elem;
}
double value()
{
return static_cast<double>(sum)/static_cast<double>(num);
}
operator double()//重载的好处，简洁！
{
return static_cast<double>(sum)/static_cast<double>(num);
}
private:
long num;
long sum;
};
template<typename T1>
auto add(T1 &a)->decltype(a+10){
return a+=10;
}
template<class T>
class AddValue
{
public:
AddValue(const T& v):theValue(v){}
void operator() (T& elem)const
{
elem+=theValue;
}
private:
T theValue;
};
int main()
{
vector<int> myvector;
myvector.push_back(10);
myvector.push_back(20);
myvector.push_back(30);
cout << "myvector contains:";
for_each (myvector.begin(), myvector.end(), myfunction);
// or:
cout << "\nmyvector contains:";
for_each (myvector.begin(), myvector.end(), myobject);
cout << endl;
MeanVlaue mv=for_each(myvector.begin(),myvector.end(),MeanVlaue());
cout<<"MeanValue:"<<mv.value()<<endl;
for_each(myvector.begin(), myvector.end(), add<int>);//参数可以自己改，eg：*(myvector.begin())
for_each (myvector.begin(), myvector.end(), myobject);
cout << endl;
double mv2=for_each(myvector.begin(),myvector.end(),MeanVlaue());
cout<<"MeanValue:"<<mv2<<endl;
return 0;
}
myvector contains: 10 20 30
myvector contains: 10 20 30
MeanValue:20
20 30 40
MeanValue:30
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```java
#include<iostream>
#include<functional>
using namespace std;
template<typename T>
T use_f(T x,function<T(T)> f){
static int count=0;
++count;
cout<<"count = "<<count
<<" &count = "<<&count<<endl;
return f(x);
}
class Fp{
private:
double p;
public:
Fp(double _p):p(_p){}
double operator()(double x){return x*p;}
};
double dub(double u){
return u*u;
}
int main(){
//lambda
cout<<use_f<double>(0.5,[](double u){return u*u;})<<endl;
//class
cout<<use_f<double>(0.5,Fp(0.5))<<endl;
//function
cout<<use_f<double>(0.5,dub)<<endl;
}
count = 1 &count = 0x10e73c260
0.25
count = 2 &count = 0x10e73c260
0.25
count = 3 &count = 0x10e73c260
0.25
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#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
#define all(x) x.begin(),x.end()
int main(){
vector<int> vec1(10,10),vec2(10,11);
for_each(all(vec1),[](int x){cout<<x<<" ";});cout<<endl;
cout<<0<<endl;
transform(all(vec1),vec1.begin(),[](int x){return x*x;});
cout<<1<<endl;
for_each(all(vec1),[](int x){cout<<x<<" ";});cout<<endl;
cout<<2<<endl;
transform(all(vec1),vec2.begin(),vec1.begin(),[](int x,int y){return x*y;});
cout<<3<<endl;
for_each(all(vec1),[](int x){cout<<x<<" ";});cout<<endl;
cout<<4<<endl;
}
10 10 10 10 10 10 10 10 10 10
0
1
100 100 100 100 100 100 100 100 100 100
2
3
1100 1100 1100 1100 1100 1100 1100 1100 1100 1100
4
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#include<bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define pb push_back
template<typename T>
void out(T x){
cout<<x<<" ";
}
int fun(int x,int y){
return x*y;
}
bool mod2(int x){
return x%2==0;
}
class Test{
public:
bool operator()(int x) {
return x%2==0;
}
};
int main(){
srand((unsigned)time(NULL));
vector<int> vec;
cout<<vec.capacity()<<endl;
cout<<vec.max_size()<<endl;
//1e9 is the max_size
vec.reserve(100);
cout<<vec.size()<<endl;
//reserve doesn't make the size
vec.resize(100);
cout<<vec.size()<<endl;
//resize will make the size
vec.clear();
cout<<vec.capacity()<<endl;
cout<<vec.size()<<endl;
vec.pb(1);
vec.pb(3);
vec.pb(2);
for_each(all(vec),out<int>);
cout<<endl;
vector<int> vec2(vec);
reverse(all(vec));
for_each(all(vec),out<int>);
cout<<endl;
vec.clear();
vec.resize(3);
swap_ranges(all(vec2),vec.begin());//will be
for_each(all(vec),out<int>);
cout<<endl;
cout<<accumulate(all(vec),1,fun)<<endl;
Test t;
cout<<t.operator()(2)<<endl;
generate(all(vec),rand);
cout<<endl;
for_each(all(vec),out<int>);
cout<<endl;
cout<<"numbers can divide 2 are "<<count_if(all(vec),mod2)<<endl;
}
#include <iostream>
#include <vector>
using namespace std;
#define all(x) x.begin(),x.end()
#define pb push_back
template<typename T>
void out(T x){
cout<<x<<" ";
}
int fun(int x,int y){
return x*y;
}
bool mod2(int x){
return x%2==0;
}
class Test{
public:
bool operator()(int x) {
return x%2==0;
}
};
int main(){
srand((unsigned)time(NULL));
vector<int> vec;
cout<<vec.capacity()<<endl;
cout<<vec.max_size()<<endl;
//1e9 is the max_size
vec.reserve(100);
cout<<vec.size()<<endl;
//reserve doesn't make the size
vec.resize(100);
cout<<vec.size()<<endl;
//resize will make the size
vec.clear();
cout<<vec.capacity()<<endl;
cout<<vec.size()<<endl;
vec.pb(1);
vec.pb(3);
vec.pb(2);
for_each(all(vec),out<int>);
cout<<endl;
vector<int> vec2(vec);
reverse(all(vec));
for_each(all(vec),out<int>);
cout<<endl;
vec.clear();
vec.resize(3);
swap_ranges(all(vec2),vec.begin());//will be
for_each(all(vec),out<int>);
cout<<endl;
cout<<accumulate(all(vec),1,fun)<<endl;
Test t;
cout<<t.operator()(2)<<endl;
generate(all(vec),rand);
cout<<endl;
for_each(all(vec),out<int>);
cout<<endl;
cout<<"numbers can divide 2 are "<<count_if(all(vec),mod2)<<endl;
}
