STL(vector, list, map)

Overview:

STL is the soul of C++. Remember this, mastering the STL is master the most part of C++. Though array is more efficient than vector, vector is still the feature of C++. In this sector, we will discuss the basic usage of vector, list, and map. Simply explain these three STL. Vector is array with intelligent memory allocation/deallocation, which saves us from the size of container; List can be regarded as doubly linked list, specific feature will be covered in the code; Map is hash table, which will be frequently used in algorithm problem.

Vector:

// vector<int>: vector of int
    // vector<vector<int>>: vector of (vector of int)
    // vector<int *>: the vector of pointers to int
    // vector<vector<int> *>: vector of pointers to vector of int


    // vector
    vector<int> V1 {3, 4, 5, 6, 7};
    // 5 5 3 7
    cout << V1.size() << " " << V1[2] << " " << V1.front() << " " << V1.back() << endl;

    // 10 elements; all with initial value 3
    vector<int> V2(10, 3);
    // 6 elements; all with initial value 0
    vector<int> V3(6);

    // add new element 8 to the back of the vector
    V1.push_back(8);

    //remove the last element of the vector
    V1.pop_back();
    
    // print the vector

    // call by value
    // 3 4 5 6 7 8
    for(int i : V1){ cout << i << " "; i++; }
    cout << endl;
    // The same as above
    // 3 4 5 6 7 8
    for(int i : V1){ cout << i << " "; }
    cout << endl;

    // call by reference
    // 3 4 5 6 7 8 
    for(int &i : V1){ cout << i << " "; i++; }
    cout << endl;
    // 4 5 6 7 8 9
    for(int i : V1){ cout << i << " "; }
    cout << endl;

    // Iterator
    // begin() returns the address of the first element
    // endI() returns the address AFTER the last element
    vector<int>::iterator it1 = V1.begin(), it2 = V1.end();
    auto it3 = V1.begin();

    for(auto it6 = V1.begin(); it6 != V1.end(); it6++){
        cout << *it6 << " ";
    }
    
    auto it10 = V1.begin() + 10;
    // auto can be very handful
    // map<int , vector<list<int*> *>:: iterator it5 = M1.begin();
    // auto it5 = M1.end()

List:

 	// list: similar to douly linked list
    list<int> L1{10, 11, 12, 13, 14};
    //does not support subscript as ina array or vector
    cout << L1.size() << " " << L1.front() << " " << L1.back() << endl;

    L1.push_back(100);
    L1.pop_back();

    L1.push_front(200);
    L1.pop_front();
    for(auto i : L1){ cout << i << " "; }
    cout << endl;

    // only list support sort, not vector
    L1.sort();
    for(auto it7 = L1.begin(); it7 != L1.end(); it7++){ cout << *it7 << " ";}
    cout << endl;
    
    // return the first address of the first match or V1.end() if no match
    auto it8 = find(V1.begin(), V1.end(), 5);
    if(it8 != V1.end())
        V1.erase(it8);
    //v1.begin() can be written as begin(V1)

    // [begin(), end())
    auto it9 = find(L1.begin(), L1.end(), 12);
    if(it9 != L1.end() )    L1.erase(it9);

    // it would compile
    // auto it11 = L1.begin() + 1;
    // it only allow ++ / --, like linked list, it only allows forward or backward
    auto it11 = L1.begin()++;

    // only list support remove
    // delete the first element with value 14
    // doing nothing if no mtach
    L1.remove(14);

Map:

    // map
    map<int, string> M1{{25, "Mary"}, {11, "Dan"}, {6, "Sanjay"} };
    // Dan
    cout << M1[11] << endl;
    // the two data items are referred to as key and value
    // adding {35, "Steve"} to M1
    M1[35] = "Steve";

    // update {25, "Nancy"} to M1
    M2[25] = "Nancy";

    // when you insert item to map, it will automatically sort by key
    for(auto i : M1) {
        cout << i.first << " " << i.second << "     ";
    }

    for(auto it12 = M1.begin(); it12 != M1.end(); it12++){
        cout << (*it12).first << " " << (*it12).second << "     ";
    }

    for(auto it12 = M1.begin(); it12 != M1.end(); it12++){
        cout << it12->first << " " << it12->second << "     ";
    }

Complete Code:

//STL Standard Template Liabrary
#include <iostream>
// container: vector, list, map, set, queue, stack, array, etc.
#include <vector>
#include <list>
#include <map>
#include <string>

using namespace std;

// the same as void f1(int* A)
void f1(int A[]){
    // it won't work, because it only pass the address
    // it's a MUST to pass the size to the function.
    // the function should be:
    // void f1(int A[], int size)
    cout << sizeof(A) / sizeof(int) << endl;
}

//


int main(){
    int A[10];
    // to get the size of array A
    cout << sizeof(A) / sizeof(int) << endl;

    string s1 = "This is very useful!";

    //================================STL===========================================


    // vector<int>: vector of int
    // vector<vector<int>>: vector of (vector of int)
    // vector<int *>: the vector of pointers to int
    // vector<vector<int> *>: vector of pointers to vector of int


    // vector
    vector<int> V1 {3, 4, 5, 6, 7};
    // 5 5 3 7
    cout << V1.size() << " " << V1[2] << " " << V1.front() << " " << V1.back() << endl;

    // 10 elements; all with initial value 3
    vector<int> V2(10, 3);
    // 6 elements; all with initial value 0
    vector<int> V3(6);

    // add new element 8 to the back of the vector
    V1.push_back(8);

    //remove the last element of the vector
    V1.pop_back();
    
    // print the vector

    // call by value
    // 3 4 5 6 7 8
    for(int i : V1){ cout << i << " "; i++; }
    cout << endl;
    // The same as above
    // 3 4 5 6 7 8
    for(int i : V1){ cout << i << " "; }
    cout << endl;

    // call by reference
    // 3 4 5 6 7 8 
    for(int &i : V1){ cout << i << " "; i++; }
    cout << endl;
    // 4 5 6 7 8 9
    for(int i : V1){ cout << i << " "; }
    cout << endl;

    // Iterator
    // begin() returns the address of the first element
    // endI() returns the address AFTER the last element
    vector<int>::iterator it1 = V1.begin(), it2 = V1.end();
    auto it3 = V1.begin();

    for(auto it6 = V1.begin(); it6 != V1.end(); it6++){
        cout << *it6 << " ";
    }
    
    auto it10 = V1.begin() + 10;
    // auto can be very handful
    // map<int , vector<list<int*> *>:: iterator it5 = M1.begin();
    // auto it5 = M1.end()



    // list: similar to douly linked list
    list<int> L1{10, 11, 12, 13, 14};
    //does not support subscript as ina array or vector
    cout << L1.size() << " " << L1.front() << " " << L1.back() << endl;

    L1.push_back(100);
    L1.pop_back();

    L1.push_front(200);
    L1.pop_front();
    for(auto i : L1){ cout << i << " "; }
    cout << endl;

    // only list support sort, not vector
    L1.sort();
    for(auto it7 = L1.begin(); it7 != L1.end(); it7++){ cout << *it7 << " ";}
    cout << endl;
    
    // return the first address of the first match or V1.end() if no match
    auto it8 = find(V1.begin(), V1.end(), 5);
    if(it8 != V1.end())
        V1.erase(it8);
    //v1.begin() can be written as begin(V1)

    // [begin(), end())
    auto it9 = find(L1.begin(), L1.end(), 12);
    if(it9 != L1.end() )    L1.erase(it9);

    // it would compile
    // auto it11 = L1.begin() + 1;
    // it only allow ++ / --, like linked list, it only allows forward or backward
    auto it11 = L1.begin()++;

    // only list support remove
    // delete the first element with value 14
    // doing nothing if no mtach
    L1.remove(14);



    // map
    map<int, string> M1{{25, "Mary"}, {11, "Dan"}, {6, "Sanjay"} };
    // Dan
    cout << M1[11] << endl;
    // the two data items are referred to as key and value
    // adding {35, "Steve"} to M1
    M1[35] = "Steve";

    // update {25, "Nancy"} to M1
    M2[25] = "Nancy";

    // when you insert item to map, it will automatically sort by key
    for(auto i : M1) {
        cout << i.first << " " << i.second << "     ";
    }

    for(auto it12 = M1.begin(); it12 != M1.end(); it12++){
        cout << (*it12).first << " " << (*it12).second << "     ";
    }

    for(auto it12 = M1.begin(); it12 != M1.end(); it12++){
        cout << it12->first << " " << it12->second << "     ";
    }


    return 0;
}