向量与动态数组相同,具有在插入或删除元素时自动调整自身大小的能力,并且容器自动处理其存储。
vector::begin()
begin()函数用于返回指向向量容器的第一个元素的迭代器。 begin()函数将双向迭代器返回到容器的第一个元素。
用法:
vectorname.begin() 参数: No parameters are passed. 返回: This function returns a bidirectional iterator pointing to the first element.
例子:
Input :myvector{1, 2, 3, 4, 5}; myvector.begin(); Output:returns an iterator to the element 1 Input :myvector{"This", "is", "Geeksforgeeks"}; myvector.begin(); Output:returns an iterator to the element This
错误和异常
1.它没有异常抛出保证。
2.传递参数时显示错误。
// INTEGER VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of begin() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
// declaration of vector container
vector<int> myvector{ 1, 2, 3, 4, 5 };
// using begin() to print vector
for (auto it = myvector.begin();
it != myvector.end(); ++it)
cout << ' ' << *it;
return 0;
}
输出:
1 2 3 4 5
// STRING VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of begin() function
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
// declaration of vector container
vector<string> myvector{ "This", "is",
"Geeksforgeeks" };
// using begin() to print vector
for (auto it = myvector.begin();
it != myvector.end(); ++it)
cout << ' ' << *it;
return 0;
}
输出:
This is Geeksforgeeks
时间复杂度:O(1)
vector::end()
end()函数用于返回指向向量容器最后一个元素旁边的迭代器。 end()函数返回双向迭代器。
用法:
vectorname.end() 参数: No parameters are passed. 返回: This function returns a bidirectional iterator pointing to next to last element.
例子:
Input :myvector{1, 2, 3, 4, 5}; myvector.end(); Output:returns an iterator after 5 Input :myvector{"computer", "science", "portal"}; myvector.end(); Output:returns an iterator after "portal"
错误和异常
1.它没有异常抛出保证。
2.传递参数时显示错误。
// INTEGER VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of end() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
// declaration of vector container
vector<int> myvector{ 1, 2, 3, 4, 5 };
// using end() to print vector
for (auto it = myvector.begin();
it != myvector.end(); ++it)
cout << ' ' << *it;
return 0;
}
输出:
1 2 3 4 5
// STRING VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of end() function
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
// declaration of vector container
vector<string> myvector{ "computer",
"science", "portal" };
// using end() to print vector
for (auto it = myvector.begin();
it != myvector.end(); ++it)
cout << ' ' << *it;
return 0;
}
输出:
computer science portal
时间复杂度:O(1)
相关用法
注:本文由纯净天空筛选整理自AyushSaxena大神的英文原创作品 vector::begin() and vector::end() in C++ STL。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。