Lanqiao cup provincial training camp - commonly used STL

The dynamic array

using namespace std;
#include<vector>
vector<T>vec;//C++ Method of directly constructing a dynamic array in 

Storing custom types with dynamic arrays

struct Student {
    
    string name;  //  name 
    int age;      //  Age 
};
int main() {
    
    vector<Student> class1;  //  class 
    Student stu1, stu2;      //  Student 1, Student 2
    stu1.name = "xiaohong";
    stu1.age = 12;
    stu2.name = "yuhaoran";
    stu2.age = 25;
    class1.push_back(stu1);
    class1.push_back(stu2);
    return 0;
}

Constructor of dynamic array

int n = 10;
// The default initial value is 0
// Define an initial value as 0  The length of is n Dynamic array of tys
vector<int>tys(n);
// Define an initial value as 1  The length of is n Dynamic array of vec
vector<int> vec(n, 1);

The above code shows how to create a length of n The initial values of are all 1 Dynamic array of .

Two bit dynamic array

int n = 5;
vector<vector<int> > vec2;
for (int i = 0; i < n; i++) {
    
    vector<int> x(n, 1); // One dimensional assignment is required 
    vec2.push_back(x);
}
for (int i = 0; i < n; i++) {
    
    for (int j = 0; j < vec2[i].size(); i++) {
    
        cout << vec2[i][j] << " ";
    }
    cout << endl;
}

Construct a n That's ok m Dynamic array of columns

//vector<vector<int> >vec(n,vector<int>(m,0));
int main(){
    
	int n= 5,m = 5;// Definition 5 That's ok 5 Column dynamic array   Printout 
	vector<vector<int> >vec(n,vector<int>(m,0));
	for(int i=0;i<vec.size();i++){
    
		for(int j=0;j<vec[0].size();j++)
			cout<<vec[i][j]<<" ";
		cout<<endl;
	}
	return 0;
}

The use of two-dimensional dynamic arrays

#include <iostream>
#include <vector>
using namespace std;
int main() {
    
    vector<vector<int> > v2d;// Define a two-dimensional dynamic array 
    for (int i = 0; i < 5; i++) {
    
        v2d.push_back(vector<int>());// Initialize 2D array   Every dimension is empty vector<int>()
    }
    for (int i = 0; i < v2d.size(); i++) {
    
        for (int j = 0; j <= i; j++) {
    
            v2d[i].push_back((i + 1) * (j + 1));  // The first j That's ok push go in j Number 
        }
    }
    for (int i = 0; i < v2d.size(); i++) {
     // Printout 
        for (int j = 0; j < v2d[i].size(); j++) {
    
            cout << i + 1 << " * " << j + 1 << " = " << v2d[i][j] << "\t";
        }
        cout << endl;
    }
    return 0;
}

aggregate set

Construct a set

using namespace std;
#include<set>
set<int>myset;// When initializing  set It's an empty set 

set The main use of

#include <iostream>
#include <string>
#include <set>
using namespace std;
int main() {
    
    set<string> country;
    country.insert("China");
    country.insert("America");
    country.insert("France");
    set<string>::iterator it;
    for (it = country.begin(); it != country.end(); it++) {
    
        cout << *it << " ";
    }
    cout << endl;
    country.erase("America");
    country.erase("England");
    if (country.count("China")) {
    
        cout << "China in country." << endl;
    }
    country.clear();
    return 0;
}

C++ in set It's traversing from small to large ,set It will sort automatically

The default data type has size rules set It can sort automatically

For user-defined data types , You need to use operator overloading

struct Node {
    
    int x, y;
    // An important knowledge point   Built in comparison function 
    bool operator<(const Node &rhs) const {
    
        if (x != rhs.x) 
            return x < rhs.x;
         else 
            return x < rhs.x;
    }
};

The mapping table map

map It means key To value The mapping relation of

key The set of is called the set of keys ,value The set of is called the set of values

Construct a mapping

#include<map>
using namespace std;
map<stirng,int>types;

stay C++ in map The traversal of is also from small to large according to the key

map Use

#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
    
    map<string, int> dict;
    dict["Tom"] = 1; // or write as dict.insert(make_pair("Tom",1));
    dict["Jone"] = 2;
    dict["Mary"] = 1;
    if (dict.count("Mary")) {
    
        cout << "Mary is in class " << dict["Mary"];
        dict["Mary"] = 5;
    }
    // Traverse map  The element pointed to by the iterator here is a pair, Yes first and second Two member variables , Each represents a mapping 
    for (map<string, int>::iterator it = dict.begin(); it != dict.end(); it++) {
    
        cout << it->first << " is in class " << it->second << endl;
    }
    dict.clear();
    return 0;
}

difficulty ： A two-dimensional map

#include <iostream>
#include <map>
#include <string>
using namespace std;
int main() {
    
	// Define a two-dimensional map "> >" There must be a space between 
    map<int, map<string, int> > info;
    int n; cin >> n;
    for (int i = 0; i < n; i++) {
    
        int class_id;  string name;
        cin >> class_id >> name;
        info[class_id][name]++;
    }
    for (map<int, map<string, int> >::iterator it1 = info.begin(); it1 != info.end(); it1++) {
    
        for (map<string, int>::iterator it2 = it1->second.begin(); it2 != it1->second.end(); it2++) {
    
            cout << "There are " << it2->second << " people named " << it2->first << " in class " << it1->first << endl;
        }
    }
    return 0;
}

/* 6 1 liu 2 bai 2 liu 3 yan 4 yan 1 bai There are 1 people named bai in class 1 There are 1 people named liu in class 1 There are 1 people named bai in class 2 There are 1 people named liu in class 2 There are 1 people named yan in class 3 There are 1 people named yan in class 4 */

Print sawtooth matrix

#include<iostream>
#include<vector>
using namespace std;

int main(){
    
	int n,m;cin>>n>>m;
	vector<vector<int> >a(n,vector<int>());// Initialize a program with n Dynamic array of rows 
	int x,y;
	for(int i=1;i<=m;i++){
    
		cin>>x>>y;
		a[x-1].push_back(y);
	}
	for(int i=0;i<a.size();i++){
    
		// If there is no element in a line   Then output a blank line 
		if(a[i].size() == 0){
    
			cout<<endl;
			continue;
		}
		for(int j=0;j<a[i].size()-1;j++) cout<<a[i][j]<<" ";
		cout<<a[i][a[i].size()-1]<<endl;
	}
	return 0;
}

Garlic gentleman solved the case

#include<iostream>
#include<set>
using namespace std;

typedef struct person{
      // Define a structure   Store everyone's height   weight   Age 
	int x,y,z;
	// Operator overloading  set It is automatically sorted   Structure must define a sort operator 
	bool operator<(const person &p) const{
    
		if(x != p.x) return x < p.x;
		else if(y != p.y) return y < p.y;
		else return z < p.z;
	}
}person;

int main(){
    
	set<person>city;// Define a person A collection of structures 
	int n,m;cin>>n>>m;
	int x,y,z;
	for(int i=1;i<=n;i++){
    
		person a;cin>>a.x>>a.y>>a.z;
		city.insert(a);// Insert into collection 
	}
	for(int i=1;i<=m;i++){
    
		person b;
		cin>>b.x>>b.y>>b.z; // Judge b Is it gathering city in 
		if(city.count(b)) cout<<"yes"<<endl;
		else cout<<"no"<<endl;
	}
	return 0;
}

Garlic King's collection

#include<iostream>
#include<map>
using namespace std;

int main(){
    
	map<string, int> T;// Establish a mapping relationship between book title and quantity 
	int n;cin>>n;string b;
	for(int i=1;i<=n;i++){
    
		cin>>b;T[b]++;
	}
	cout<<T.size()<<endl;
	// Pay attention to traversing map The technique of  it != T.end()
	for(map<string, int>::iterator it = T.begin();it != T.end();it++){
    
		cout<<it->first<<" "<<it->second<<endl;
	}
	return 0;
}