在 C++ 中显示矢量容器的内容
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Displaying contents of a vector container in C++
提问by heapuser
The following is a C++ program using STL vector container. Just wanted to know why the display() function is not printing the vector contents to the screen. If displaying the size() line is commented out, display() function works fine.
下面是一个使用 STL 向量容器的 C++ 程序。只是想知道为什么 display() 函数没有将矢量内容打印到屏幕上。如果显示 size() 行被注释掉，则 display() 函数工作正常。
#include <iostream>
#include <vector>
using namespace std;
void display(vector<int> &v)
{
for(int i; i<v.size(); i++)
{
cout << v[i] << " ";
}
cout << "\n" << endl;
}
int main()
{
vector<int> v;
cout << "Size of Vector=" << v.size() << endl;
//Putting values into the vector
int x;
cout << "Enter five integer values" << endl;
for(int i; i<5; i++)
{
cin >> x;
v.push_back(x);
}
//Size after adding values
cout << "Size of Vector=" << v.size() << endl;
//Display the contents of vector
display(v);
v.push_back(6);
//Size after adding values
cout << "Size of Vector=" << v.size() << endl;
//Display the contents of vector
display(v);
}
Output:
输出：
Size of Vector=0
Enter five integer values
1
2
3
4
5
Size of Vector=5
Size of Vector=6
回答by 111111
There is an idiomatic way for printing a vector out.
有一种惯用的方式打印矢量。
#include <algorithm>
#include <iterator>
//note the const
void display_vector(const vector<int> &v)
{
std::copy(v.begin(), v.end(),
std::ostream_iterator<int>(std::cout, " "));
}
This way is safe and doesn't require you to keep track of the vectors size or anything like that. It is also easily recognisable to other C++ developers.
这种方式是安全的，不需要您跟踪向量大小或类似的东西。它也很容易被其他 C++ 开发人员识别。
This method works on other container types too that do not allow random access.
此方法也适用于不允许随机访问的其他容器类型。
std::list<int> l;
//use l
std::copy(l.begin(), l.end(),
std::ostream_iterator<int>(std::cout, " "));
This works both ways with input too consider the following:
这适用于输入的两种方式也请考虑以下事项：
#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>
int main()
{
std::cout << "Enter int end with q" << std::endl;
std::vector<int> v; //a deque is probably better TBH
std::copy(std::istream_iterator<int>(std::cin),
std::istream_iterator<int>(),
std::back_inserter<int>(v));
std::copy(v.begin(), v.end(),
std::ostream_iterator<int>(std::cout, " "));
}
This version doesn't require any hard coding of size or manual management of the actual elements.
此版本不需要任何大小的硬编码或实际元素的手动管理。
回答by YXD
You are not initializing your variables. for(int i = 0;not for(int i;
您没有初始化变量。for(int i = 0;不是for(int i;
回答by jjf
I think this is the easiest way to go:
我认为这是最简单的方法：
#include <iostream>
#include <vector>
using namespace std;
int main(){
vector<int> v;
int x;
cout << "Enter five integer values" << endl;
for(int i=0; i<5; i++)
{
cin >> x;
v.push_back(x);
}
for (int i = 0; i < (int)v.size(); i++)
cout<< v.at(i) <<endl;
}
回答by Spandyie
I have found printing using for_each() very easy to understand and intuitive
我发现使用 for_each() 打印非常容易理解和直观
#include<vector>
#include<algorithm>
using namespace std;
main(){
vector<int> foo_bar{1,2,3,4,5};
auto print_array = [](const auto& o) {cout << o << " "; };
for_each(foo_bar.begin(), foo_bar.end(), print_array);
}
回答by Nahid Hasan
If you use compiler versions g++ 11 or more than then you simply use:
如果您使用编译器版本 g++ 11 或更高版本，则只需使用：
#include <iostream>
#include <vector>
using namespace std;
int main(){
vector<int> v;
int x;
cout << "Enter five integer values" << endl;
for(int i=0; i<5; i++)
{
cin >> x;
v.push_back(x);
}
for (auto i: v)
cout<< i <<endl;
}
