vector often called a container, as a vector to accommodate other elements, all the elements of the same type. Each element has an associated index corresponding to the index used to access elements. Briefly, vector is a dynamic array can store many types of data, the position of the elements which are contiguous in memory.
Include the header file:
#include <vector> using namespace std;
vector class is a template, it is necessary to provide the type of object stored within the vector instantiation:
vector<int> ivec; vector<string> file;
Definition and initialization vector objects
Vector <T> V1; // V1 is a null vector, the elements of its potential T-type Vector <T> V2 (V1); // equivalent to Vector <T> V1 = V2 Vector <T> V3 (n-, Val); // V3 contains n elements, each of Val Vector <T> V4 (n); // V4 has n element values is performed initialization vector <T> v5 {a, b, c, ......} D; // V5 elements comprising the initial number of values, each element is assigned a corresponding initial value, equivalent to the vector <T> v5 = {a , b, c, d ......}
vector <T> v1, v1 does not contain any element, an empty container, it seems useless, but the program can be efficiently added to the vector elements at runtime, which is in fact a common method, defined as the ratio the size of the container is more efficient.
Initialization list or the number of elements?
Vector <T> V1 ( 10 ); // V1 has 10 elements, each values are 0 Vector <T> V2 { 10 }; // V2 elements have a value of 10 Vector <T> V3 ( 10 , 1 ); // V3 has 10 elements, each value of a Vector <T> V4 ( 10 , 1 ); // V4 has two elements, values of 10 and 1, respectively,
If you are using parentheses, it can be said value is used to construct vector objects; if it is braces, we can say we want the list to initialize the vector objects, that is, the initialization process will try to put a value in braces as handle element initial value, the initialization mode will be considered only when other types do not correspond. The vector <string> v8 {10, "hi"}; // v8 has the value 10 "hi" element.
Adding elements to a vector object
vector push_back member function responsible for as a value on a vector to the end of the last element vector pressed object.
vector < int > v2; // empty vector objects for ( int I = 0 ; I =! 100 ; I ++ ) v2.push_back (I); // sequentially into the integer v2 tail
Other vector operations
v.empty (); // if v does not contain any element, returns true; false otherwise v.size (); // returns the number of elements in v v [n]; // Returns the n th position v the reference element <, <=,>,> =; // to compare lexicographically
Note : vector objects subscript operator can be used to access an existing element, the additional element can not be used.
vector < int > ivec; // Iveco empty vector objects for ( int I = 0; I =! 10 ; ++ I) ivec [I] = I; // error, ivec contains no elements