stl vector 函数

C ++ vector :: front()函数 (C++ vector::front() function)

vector::front() is a library function of "vector" header, it is used to access the first element from the vector, it returns a reference to the first element of the vector.

vector :: front()是“ vector”头文件的库函数，用于访问向量中的第一个元素，它返回对向量中第一个元素的引用。

Note: To use vector, include <vector> header.

注意：要使用向量，请包含<vector>标头。

Syntax of vector::front() function

vector :: front()函数的语法

    vector::front();

Parameter(s): none – It accepts nothing.

参数： 无 –不接受任何内容。

Return value: reference – It returns a reference to the first element of vector.

返回值： reference –返回对向量的第一个元素的引用。

Example:

例：

    Input:
vector<int> vector1{ 1, 2, 3, 4, 5 };
Function call:
cout << vector1.front() << endl;
Output:
1

C ++程序演示vector :: front()函数的示例 (C++ program to demonstrate example of vector::front() function)

//C++ STL program to demonstrate example of
//vector::front() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> v1{ 10, 20, 30, 40, 50 };
//accessing first element
//using vector::front() function
cout << "first element is: " << v1.front() << endl;
//changing first element
v1.at(0) = 100;
cout << "now, first element is: " << v1.front() << endl;
return 0;
}

Output

输出量

first element is: 10
now, first element is: 100

Reference: C++ vector::front()

参考： C ++ vector :: front()

翻译自: https://www.includehelp.com/stl/vector-front-function-with-example.aspx

stl vector 函数