unordered_multimap swap() function in C++ STL

Last Updated : 21 Aug, 2018

The unordered_multimap::swap() is a built-in function in C++ STL which swaps the contents of two unordered_multimap containers. The sizes can differ of both the containers. Syntax:

unordered_multimap_name1.swap(unordered_multimap_name2)

Parameters: The function accepts a single mandatory parameter unordered_multimap_name2 which specifies the unordered_multimap with which the swapping of unordered_multimap_name1 is to be done. Return Value: It does not return anything. Below programs illustrates the above function: Program 1:

CPP

// C++ program to illustrate the // unordered_multimap::swap() #include <bits/stdc++.h> using namespace std; int main() {  // declaration  unordered_multimap<int, int> sample1, sample2;  // inserts key and element  // in sample1  sample1.insert({ 10, 100 });  sample1.insert({ 50, 500 });  // inserts key and element  // in sample1  sample2.insert({ 20, 200 });  sample2.insert({ 30, 300 });  sample2.insert({ 30, 150 });  cout << "Key and Elements of Sample1 before swap are:";  for (auto it = sample1.begin(); it != sample1.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  cout << "\nKey and Elements of Sample2 before swap are:";  for (auto it = sample2.begin(); it != sample2.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  // performs swap of two  // unordered_multimaps  sample1.swap(sample2);  cout << "\n\nKey and Elements of Sample1 after swap are:";  for (auto it = sample1.begin(); it != sample1.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  cout << "\nKey and Elements of Sample2 after swap are:";  for (auto it = sample2.begin(); it != sample2.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  return 0; }

Output:

 Key and Elements of Sample1 before swap are:{50, 500} {10, 100} Key and Elements of Sample2 before swap are:{20, 200} {30, 150} {30, 300} Key and Elements of Sample1 after swap are:{20, 200} {30, 150} {30, 300} Key and Elements of Sample2 after swap are:{50, 500} {10, 100}

Program 2:

CPP

// C++ program to illustrate the // unordered_multimap::swap() #include <bits/stdc++.h> using namespace std; int main() {  // declaration  unordered_multimap<char, char> sample1, sample2;  // inserts key and element  // in sample1  sample1.insert({ 'a', 'A' });  sample1.insert({ 'g', 'G' });  // inserts key and element  // in sample1  sample2.insert({ 'b', 'B' });  sample2.insert({ 'c', 'C' });  sample2.insert({ 'd', 'D' });  cout << "Key and Elements of Sample1 before swap are:";  for (auto it = sample1.begin(); it != sample1.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  cout << "\nKey and Elements of Sample2 before swap are:";  for (auto it = sample2.begin(); it != sample2.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  // performs swap of two  // unordered_multimaps  sample1.swap(sample2);  cout << "\n\nKey and Elements of Sample1 after swap are:";  for (auto it = sample1.begin(); it != sample1.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  cout << "\nKey and Elements of Sample2 after swap are:";  for (auto it = sample2.begin(); it != sample2.end(); it++) {  cout << "{" << it->first << ", " << it->second << "} ";  }  return 0; }

Output:

 Key and Elements of Sample1 before swap are:{g, G} {a, A} Key and Elements of Sample2 before swap are:{d, D} {b, B} {c, C} Key and Elements of Sample1 after swap are:{d, D} {b, B} {c, C} Key and Elements of Sample2 after swap are:{g, G} {a, A}