unordered_multimap swap() function in C++ STL Last Updated : 21 Aug, 2018 Comments Improve Suggest changes Like Article Like Report 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} Comment More infoAdvertise with us G gopaldave Follow Improve Article Tags : Misc C++ STL CPP-Functions cpp-unordered_multimap +1 More Practice Tags : CPPMiscSTL Similar Reads Unordered Multimap in C++ STL In C++, the unordered_multimap is an unordered associative container that stores data in the form of key-value pairs. 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