C++ vector::empty()用法及代碼示例

C++ vector::empty() 函數

vector::empty() 是 "vector" 頭文件的庫函數，用於檢查給定的向量是否為空向量，如果向量大小為 0 則返回真，否則返回假。

注意：要使用矢量，請包括<vector>標題。

vector::empty() 函數的語法

    vector::empty();

參數： void– 它不接受任何參數。

返回值： bool– 如果向量大小為 0，則返回 true，否則返回 false。

例：

    Input:
    vector<int> vector1{ 1, 2, 3, 4, 5 };
    vector<int> vector2;

    Function call:
    cout << vector1.empty() << endl;
    cout << vector2.empty() << endl;

    Output:
    false
    true

C++程序演示vector::empty()函數的例子

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

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

int main()
{
    vector<int> v1;

    //printing the size of the vector
    cout << "Total number of elements:" << v1.size() << endl;
    //checking whether vector is empty or not
    if (v1.empty())
        cout << "vector is empty." << endl;
    else
        cout << "vector is not empty." << 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 of the vector
    cout << "Total number of elements:" << v1.size() << endl;
    //checking whether vector is empty or not
    if (v1.empty())
        cout << "vector is empty." << endl;
    else
        cout << "vector is not empty." << endl;

    return 0;
}

輸出

Total number of elements:0
vector is empty.
Total number of elements:5
vector is not empty.

參考：C++ vector::empty()