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::at()
at()函数用于参考在作为函数参数给出的位置上存在的元素。句法:
vectorname.at(position) 参数: Position of the element to be fetched. 返回: Direct reference to the element at the given position.
例子:
Input: myvector = 1, 2, 3 myvector.at(2); Outpu:3 Input: myvector = 3, 4, 1, 7, 3 myvector.at(3); Output: 7
错误和异常
- 如果向量中不存在该位置,则抛出out_of_range。
- 否则,它具有强大的无异常抛出保证。
// CPP program to illustrate
// Implementation of at() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> myvector;
myvector.push_back(3);
myvector.push_back(4);
myvector.push_back(1);
myvector.push_back(7);
myvector.push_back(3);
cout << myvector.at(3);
return 0;
}
输出:
7
应用范围:
给定一个整数向量,打印出现在偶数位置的所有整数。
Input: 1, 2, 3, 4, 5, 6, 7, 8, 9 Output: 1 3 5 7 9 Explanation - 1, 3, 5, 7 and 9 are at position 0, 2, 4, 6 and 8 which are even
算法
- 循环运行直到向量的大小。
- 检查该位置是否可被2整除,如果是,则在该位置打印元素。
// CPP program to illustrate
// Application of at() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> myvector;
myvector.push_back(1);
myvector.push_back(2);
myvector.push_back(3);
myvector.push_back(4);
myvector.push_back(5);
myvector.push_back(6);
myvector.push_back(7);
myvector.push_back(8);
myvector.push_back(9);
// vector becomes 1, 2, 3, 4, 5, 6, 7, 8, 9
for (int i = 0; i < myvector.size(); i += 2) {
cout << myvector.at(i);
cout << " ";
}
return 0;
}
输出:
1 3 5 7 9
vector::swap()
此函数用于将一个向量的内容与相同类型和大小的另一个向量交换。
用法:
vectorname1.swap(vectorname2) 参数: The name of the vector with which the contents have to be swapped. Result: All the elements of the 2 vectors are swapped.
例子:
Input:myvector1 = {1, 2, 3, 4} myvector2 = {3, 5, 7, 9} myvector1.swap(myvector2); Output:myvector1 = {3, 5, 7, 9} myvector2 = {1, 2, 3, 4} Input:myvector1 = {1, 3, 5, 7} myvector2 = {2, 4, 6, 8} myvector1.swap(myvector2); Output:myvector1 = {2, 4, 6, 8} myvector2 = {1, 3, 5, 7}
错误和异常
- 如果向量不是同一类型,则会引发错误。
- 否则,它具有基本的无异常抛出保证。
// CPP program to illustrate
// Implementation of swap() function
#include <iostream>
#include <vector>
using namespace std;
int main()
{
// vector container declaration
vector<int> myvector1{ 1, 2, 3, 4 };
vector<int> myvector2{ 3, 5, 7, 9 };
// using swap() function to swap
// elements of vector
myvector1.swap(myvector2);
// printing the first vector
cout << "myvector1 = ";
for (auto it = myvector1.begin();
it < myvector1.end(); ++it)
cout << *it << " ";
// printing the second vector
cout << endl
<< "myvector2 = ";
for (auto it = myvector2.begin();
it < myvector2.end(); ++it)
cout << *it << " ";
return 0;
}
输出:
myvector1 = 3 5 7 9 myvector2 = 1 2 3 4
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::at() and vector::swap() 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。