Leetcode Preparation Phase--vector

Vector is a variable size array
advantage: Find Fast, and at the end of the increase delete quickly

Implementation Principle

Vectors, like array, occupy a contiguous amount of storage space, which means they can be accessed through the offset of the pointer.
vector uses dynamic array to store data, and when the newly inserted data reaches the array's storage length, it is costly to reallocate the memory space while moving the data in the array to the new space, so the vector's real space is larger than the space needed to store the data, Allocate additional space to store data that may be stored.

Defining and initializingDefine an empty vector

Vector<t> v;

Define a vector copy

Vector<t> v1 (v);

Defined and initialized

Vector<t> V (n,i);//define a vector with a length of N and an initial value of I

Define a specific length

Vector<t> v (n);

Basic Operations

Capacity

Size (): Returns the magnitude of a vector

Empty (): Returns whether the vector is empty

Element Access

Front (): Returns the value of the first element of a vector

End (): Returns the value of the last element of a vector

Modifiers

Push_back (val): Add a new element to the vector

Pop_back (): Remove vector last element

Insert (position of vector iterator, value) or insert (position of vector iterator, length, value) or insert (position of vector iterator, position of iterator 1, position of iterator 2)

#include <iostream>
#include <vector>

int main ()
{
    std::vector<int> VEC (2);
    std::vector<int> Res;
    Std::vector<int>::iterator it = Res.begin ();
    Res.insert (it, 2);
    Res.insert (it + 2, Vec.begin (), Vec.end ());
    Res.insert (it, Vec.begin (), Vec.begin () + 2);
    return 0;
}

Traversal

There are usually two ways to traverse the iterator by using the subscript

 #include <iostream> #include <vector> int main () {std::vector<int> VEC (10
    );
    for (int i = 0; i < vec.size (); i++) {std::cout << vec[i] << Std::endl; for (Std::vector<int>::iterator it = Vec.begin (); it!= vec.end (); ++it) {std::cout <<*IT<&L T
    Std::endl;
return 0; }