[C++] STL - vector

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멤버 함수

생성

#include <vector>

using namespace std;

int main(){    
    vector<int> first;    // 빈 벡터
    vector<int> second(4, 100);    // 4개의 int(값 100)
    vector<int> third(second.begin(), second.end());    // 반복자 사용
    vector<int> fourth(third);    // 벡터 복사

    int myints[] = {1, 2, 3, 4};
    vector<int> fifth(myints, myints + sizeof(myints)/sizeof(int));    // 반복자 사용2(배열)

    return 0;
}

---

반복자

• begin() / end()
• rbegin() / rend()
• cbegin() / cend() : const * C++11
• crbegin() / crend() * C++11

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc;
    for(int i = 1; i <= 5; ++i)
        vc.push_back(i);

    for(vector<int>::iterator it = vc.begin(); it != vc.end(); ++it)
        cout<<*it<<' ';
    cout<<'\n';
    // 1 2 3 4 5
    for(vector<int>::reverse_iterator rit = vc.rbegin(); it != vc.rend(); ++rit)
        cout<<*rit<<' ';
    cout<<'\n';
    // 5 4 3 2 1

    return 0;
}

---

용량

• size()
• max_size()
• capacity()
• resize()
• empty()
• reserve() : capacity 변경
• shrink_to_fit() * C++11

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc;
    cout << vc.size() << endl;
    cout << vc.capacity() << endl;
    cout << vc.max_size() << endl;
    // 0
    // 0
    // 536870911

    for(int i = 1; i <= 5; ++i)
        vc.push_back(i);
    cout << vc.size() << endl;
    cout << vc.capacity() << endl;
    cout << vc.max_size() << endl;
    // 5 {1, 2, 3, 4, 5}
    // 8
    // 536870911

    vc.insert(vc.end(), 10, 100);
    cout << vc.size() << endl;
    cout << vc.capacity() << endl;
    cout << vc.max_size() << endl;
    // 15 {1, 2, 3, 4, 5, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100}
    // 15
    // 536870911

    vc.pop_back();
    cout << vc.size() << endl;
    cout << vc.capacity() << endl;
    cout << vc.max_size() << endl;
    // 14 {1, 2, 3, 4, 5, 100, 100, 100, 100, 100, 100, 100, 100, 100}
    // 15
    // 536870911

    return 0;
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc;
    for(int i = 1; i < 10; ++i)
        vc.push_back(i);
    // 1 2 3 4 5 6 7 8 9

    vc.resize(5);
    // 1 2 3 4 5
    vc.resize(8, 100);
    // 1 2 3 4 5 100 100 100
    vc.resize(10);
    // 1 2 3 4 5 100 100 100 0 0

    return 0;
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc;
    int sum = 0;

    for(int i = 1; i <= 10; ++i)
        vc.push_back(i);

    while(!vc.empty()){
        sum += vc.back();
        vc.pop_back();
    }

    cout << sum << endl;
    // 55

    return 0;
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc(100);
    cout << vc.capacity() << endl;
    // 100
    vc.resize(10);
    cout << vc.capacity() << endl;
    // 100
    vc.shrink_to_fit();
    cout << vc.capacity() << endl;
    // 10

    return 0;
}

---

요소 접근

• []
• at()
• front()
• back()
• data() * C++11

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc(10);
    int len = vc.size();
    for(int i = 0; i < len; ++i)
        vc.at(i) = i;

    for(int i = 0; i < len; ++i)
        cout << ' ' << vc.at(i);
    cout << endl;
    // 0 1 2 3 4 5 6 7 8 9

    cout << vc.front() << endl;
    // 0
    cout << vc.back() << endl;
    // 9

    return 0;
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc(5);
    int *p = vc.data();

    *p = 10;
    ++p;
    *p = 20;
    p[2] = 100;
    // 10 20 0 100 0

    return 0;
}

---

제어

• assign()
• push_back()
• pop_back()
• insert()
• erase()
• swap()
• clear()
• emplace() * C++11
• emplace_back() * C++11

emplace vs insert: construct vs object

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> first;
    vector<int> second;
    vector<int> third;

    first.assign(7, 100);    // 사이즈, 값
    second.assign(first.begin()+1, first.end()-1);    // 반복자, 반복자

    int arr[] = {12, 34, 56};
    third.assign(arr, arr+3);

    cout << first.size() << ' ' << second.size() << ' ' << third.size() << endl;
    // 7 5 3
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc;

    for(int i = 1; i <= 5; ++i)
        vc.push_back(i);
    // 1 2 3 4 5
    vc.pop_back();
    // 1 2 3 4
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc(3, 100);
    vc.insert(vc.begin(), 200);
    vc.insert(vc.begin(), 2, 300);
    // 300 300 200 100 100 100

    vector<int> vc2(2, 400);
    vc.insert(vc.begin() + 2, vc2.begin(), vc2.end());
    // 300 300 400 400 200 100 100 100

    int arr[] = {501, 502, 503};
    vc.insert(vc.begin(), arr, arr+3);
    // 501 502 503 300 300 400 400 200 100 100 100

    vc.erase(vc.begin()+5);
    // 501 502 503 300 300 400 200 100 100 100
    vc.erase(vc.begin()+3, vc.begin()+4);
    // 501 502 503 400 200 100 100 100

    return 0;
}

#include <iostream>
#include <vector>

using namespace std;

int main(){
    vector<int> vc1(3, 100);
    vector<int> vc2(5, 200);
    vc1.swap(vc2);

    vector<int>::iterator it;
    for(it = vc1.begin(); it != vc1.end(); ++it)
        cout << *it << ' ';
    cout << endl;
    for(it = vc2.begin(); it != vc2.end(); ++it)
        cout << *it << ' ';
    cout << endl;
    // 200 200 200 200 200
    // 100 100 100

    vc1.clear();
    vc1.push_back(1);
    for(it = dq1.begin(); it != dq1.end(); ++it)
        cout << *it << ' ';
       // 1

    return 0;
}

---

할당

• get_allocator()