C++ 如何将 vector<pair<int, int> > 传递给函数？

How can you pass a vector<pair<int, int> > into a function?

提问by Bob John

If I try to declare the function as void some_function(vector<pair<int, int> > theVector), I get an error (presumably from the comma after "pair<int." Any ideas on how I can pass this vector with pairs into a function?

如果我尝试将函数声明为void some_function(vector<pair<int, int> > theVector)，我会收到一个错误（大概是来自“ pair<int.”之后的逗号。关于如何将这个带有成对的向量传递给函数的任何想法？

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>

void someFunc(int x, int y, vector<pair<int, int> > hello);

int main()
{
    int x = 0;
    int y = 5;

    vector<pair<int, int> > helloWorld;
    helloWorld.push_back(make_pair(1,2));

    someFunc(x,y,helloWorld);
}

void someFunc(int x, int y, vector<pair<int, int> > hello)
{
    cout << "I made it." << endl;
}

Error: 'vector' has not been declared

错误：“向量”尚未声明

回答by

You failed to include <utility>, which defines std::pair, andyou're using vectorand pair, instead of std::vectorand std::pair.

您未能包含<utility>，它定义了std::pair，并且您使用的是vectorand pair，而不是std::vectorand std::pair。

All of the standard template library is inside the namespace std, so you must prefix types from the STL with std, like std::vector. An alternative would be to add using std::vector;after you include <vector>.

所有标准模板库都在命名空间内std，因此您必须在 STL 中为类型添加前缀std，例如std::vector. 另一种方法是using std::vector;在包含之后添加<vector>。

回答by billz

You need to have provide full namespace for vector, pair, make_par, they are from std namespace:

您需要为 vector、pair、make_par 提供完整的命名空间，它们来自 std 命名空间：

void someFunc(int x, int y, std::vector<std::pair<int, int> > hello);

int main()
{
    int x = 0;
    int y = 5;

    std::vector<std::pair<int, int> > helloWorld;
    helloWorld.push_back(std::make_pair(1,2));

    someFunc(x,y,helloWorld);
    return 0;
}

void someFunc(int x, int y, std::vector<std::pair<int, int> > hello)
{
    std::cout << "I made it." << std::endl;
}

Side note: you could pass vector to someFunc by reference, this will elide unnecessary copy:

旁注：您可以通过引用将 vector 传递给 someFunc，这将消除不必要的副本：

 void someFunc(int x, int y, const std::vector<std::pair<int, int> >& hello);
                              ^^^                                   ^^

回答by MahlerFive

Have you included <vector>and <utility>? You should use the std::namespace on both vectorand pair.

你包括<vector>和<utility>吗？您应该std::在vector和上都使用命名空间pair。

eg. void some_function(std::vector< std::pair<int, int> > theVector)

例如。 void some_function(std::vector< std::pair<int, int> > theVector)

edit: Of course you generally shouldn't pass in a vector by value, but by reference.

编辑：当然，您通常不应该通过值传递向量，而是通过引用传递。

eg. void some_function(std::vector< std::pair<int, int> >& theVector)

例如。 void some_function(std::vector< std::pair<int, int> >& theVector)

回答by Soroush khoubyarian

I chekced your code you just have to add the stdnamespace right below your #include. And you don't need to add #include <utility>it can work without it.
using namespace std

我检查了您的代码，您只需std在#include. 而且你不需要添加#include <utility>它可以在没有它的情况下工作。
using namespace std