C++ vector::capacity()用法及代碼示例

C++ vector::capacity() 函數

vector::capacity()是"vector"頭的庫函數，用於求向量的容量，返回當前分配給向量的存儲空間。

注意：要使用矢量，請包括<vector>標題。

vector::capacity() 函數的語法

    vector::capacity();

參數： void– 它不接受任何參數。

返回值： size_type– 它返回容量，即向量的存儲空間。

例：

    Input:
    vector<int> vector1{ 1, 2, 3, 4, 5 };

    Function call:
    cout << vector1.capacity();

    Output:
    8

C++程序演示vector::capacity()函數的例子

//C++ STL program to demonstrate example of
//vector::capacity() function

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

int main()
{
    vector<int> v1;

    //printing the size & capacity of the vector
    cout << "Total number of elements:" << v1.size() << endl;
    cout << "Storage space:" << v1.capacity() << endl;

    //pushing elements
    v1.push_back(10);
    v1.push_back(20);
    v1.push_back(30);
    v1.push_back(40);
    v1.push_back(50);

    //printing the size & capacity of the vector
    cout << "Total number of elements:" << v1.size() << endl;
    cout << "Storage space:" << v1.capacity() << endl;

    return 0;
}

輸出

Total number of elements:0
Storage space:0
Total number of elements:5
Storage space:8

參考：C++ vector::capacity()