无涯教程-C++ Multimap - swap函数 C++multimap swap()函数用于交换(或交换)两个mu

C++multimap swap()函数用于交换(或交换)两个multimap的内容，但两个multimap必须为相同类型，尽管大小可能有所不同。

swap - 语法

void swap (multimap& x);

swap - 参数

x : 用于与其交换内容的multimap集合。

swap - 例子1

让我们看一下将一个multimap的元素交换到另一个的简单示例:

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   multimap<char, int> m1 = {
      {a, 1},
      {b, 2},
      {c, 3},
      {b, 4},
      {c, 5},
      };

   multimap<char, int> m2;

   m2.swap(m1);

   cout << "Multimap m2 contains following elements" << endl;

   for (auto it = m2.begin(); it != m2.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

输出:

Multimap m2 contains following elements
a = 1
b = 2
b = 4
c = 3
c = 5

在上面的示例中，multimapm1具有五个元素，而m2为空。当您将m1交换为m2时，m1的所有元素都将交换为m2。

swap - 例子2

让我们看一个简单的示例来交换两个multimap的内容:

#include <iostream>
#include <map>

using namespace std;

int main ()
{
  multimap<char,int> multimap1,multimap2;

  multimap1 = {
              {x, 100},
              {x, 200}
              };

  multimap2 = {
              {a, 110},
              {b, 220},
              {a, 330}
              };

  multimap1.swap(multimap2);

  cout << "multimap1 contains:\n";
  for (multimap<char,int>::iterator it=multimap1.begin(); it!=multimap1.end(); ++it)
    cout << it->first << " => " << it->second << 
;

  cout << "multimap2 contains:\n";
  for (multimap<char,int>::iterator it=multimap2.begin(); it!=multimap2.end(); ++it)
    cout << it->first << " => " << it->second << 
;

  return 0;
}

输出:

multimap1 contains:
a => 110
a => 330
b => 220
multimap2 contains:
x => 100
x => 200

在上面的例子中，两个multimap的内容，即multimap1和multimap2相互交换。

swap - 例子3

让我们看一个简单的示例来交换两个multimap的内容:

#include<iostream>
#include<map>

using namespace std;
 
int main()
{
   //Take any two multimaps
    multimap<int, char> multimap1, multimap2;
 
    multimap1 = {
                {1, a},
                {2, b},
                {2, c},
                {4, d} };
 
    multimap2 = {
                {1, x},
                {2, y},
                {2, z} };
 
   //Swap elements of multimaps
    swap(multimap1, multimap2);
 
   //Print the elements of multimaps
    cout << "multimap1:\n"<< "\tKEY\tELEMENT\n";
    for (auto it = multimap1.begin();
         it != multimap1.end(); it++)
 
        cout << "\t" << it->first << "\t" << it->second << 
;
 
    cout << "multimap2:\n"<< "\tKEY\tELEMENT\n";
    for (auto it = multimap2.begin();
         it != multimap2.end(); it++)
 
        cout << "\t" << it->first << "\t" << it->second << 
;
 
    return 0;
}

输出:

multimap1:
	KEY	ELEMENT
	1	x
	2	y
	2	z
multimap2:
	KEY	ELEMENT
	1	a
	2	b
	2	c
	4	d

在上面的示例中，另一种形式的swap()函数用于交换两个multimap的内容。

swap - 例子4

让我们看一个简单的例子:

#include <iostream>
#include <string>
#include <map>

using namespace std;

void show(const char *msg, multimap<string, int> mp);

int main() {
  multimap<string, int> m1, m2;

  m1.insert(pair<string, int>("A", 100));
  m1.insert(pair<string, int>("B", 300));
  m1.insert(pair<string, int>("B", 200));

 //Exchange the contents of m1 and m2.
  cout << "Exchange m1 and m2.\n";
  m1.swap(m2);
  show("Contents of m2: ", m2);
  show("Contents of m1: ", m1);

//Clear m1.
  m1.clear();
  if(m1.empty()) cout << "m1 is now empty.";

  return 0;
}

// Display the contents of a multimap<string, int> by using an iterator.
void show(const char *msg, multimap<string, int> mp) {
  multimap<string, int>::iterator itr;

  cout << msg << endl;
  for(itr=mp.begin(); itr != mp.end(); ++itr)
    cout << "  " << itr->first << ", " << itr->second << endl;
  cout << endl;
}

输出:

Exchange m1 and m2. Contents of m2: A, 100 B, 300 B, 200

Contents of m1:

m1 is now empty.

在上面的示例中，将multimapm1的内容交换到multimapm2，并且在清除了交换m1后，multimap已被清除。

无涯教程-C++ Multimap - swap函数