**Symmetric difference of two sorted ranges**

The symmetric difference of two sets is formed by the elements that are present in one of the sets, but not in the other. Among the equivalent elements in each range, those discarded are those that appear before in the existent order before the call. The existing order is also preserved for the copied elements.

The elements are compared using operator< for the first version, and comp for the second. Two elements, a and b are considered equivalent if (!(a<b) && !(b<a)) or if (!comp(a, b) && !comp(b, a)).

The elements in the ranges shall already be ordered.

1. **Using default operator< :**

Syntax :

Template :OutputIterator set_symmetric_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result);Parameters :first1, last1Input iterators to the initial and final positions of the first sorted sequence. The range used is [first1, last1), which contains all the elements between first1 and last1, including the element pointed by first1 but not the element pointed by last1.first2, last2Input iterators to the initial and final positions of the second sorted sequence. The range used is [first2, last2).resultOutput iterator to the initial position of the range where the resulting sequence is stored. The pointed type shall support being assigned the value of an element from the other ranges.compBinary function that accepts two arguments of the types pointed by the input iterators, and returns a value convertible to bool. The function shall not modify any of its arguments. This can either be a function pointer or a function object.The ranges shall not overlap.Return Type :An iterator to the end of the constructed range.

// CPP program to illustrate // std :: set_symmetric_difference #include <iostream> // std::cout #include <algorithm> // std::set_symmetric_difference, std::sort #include <vector> // std::vector // Driver code int main() { int first[] = { 5, 10, 15, 20, 25 }; int second[] = { 50, 40, 30, 20, 10 }; int n = sizeof(first) / sizeof(first[0]); // Print first array std::cout << "First array contains :"; for (int i = 0; i < n; i++) std::cout << " " << first[i]; std::cout << "\n"; // Print second array std::cout << "Second array contains :"; for (int i = 0; i < n; i++) std::cout << " " << second[i]; std::cout << "\n\n"; std::vector<int> v(10); std::vector<int>::iterator it, st; // Sorting both the arrays std::sort(first, first + 5); std::sort(second, second + 5); // Using default operator< it = std::set_symmetric_difference(first, first + 5, second, second + 5, v.begin()); std::cout << "The symmetric difference has " << (it - v.begin()) << " elements:\n"; for (st = v.begin(); st != it; ++st) std::cout << ' ' << *st; std::cout << '\n'; return 0; }

Output:

First array contains : 5 10 15 20 25 Second array contains : 50 40 30 20 10 The symmetric difference has 6 elements: 5 15 25 30 40 50

2. **Using custom function :**

Synatx :

Template :OutputIterator set_symmetric_difference (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);Parameters :first1, last1, first2, last2, result are same as described above.compBinary function that accepts two arguments of the types pointed by the input iterators, and returns a value convertible to bool. The function shall not modify any of its arguments. This can either be a function pointer or a function object.The ranges shall not overlap.Return Type :An iterator to the end of the constructed range.

// CPP program to illustrate // std :: set_symmetric_difference #include <iostream> // std::cout #include <algorithm> // std::set_symmetric_difference, std::sort #include <vector> // std::vector // Custom function bool comp(int a, int b) { return a < b; } // Driver code int main() { int first[] = { 5, 10, 15, 20, 25 }; int second[] = { 50, 40, 30, 20, 10 }; int n = sizeof(first) / sizeof(first[0]); // Print first array std::cout << "First array contains :"; for (int i = 0; i < n; i++) std::cout << " " << first[i]; std::cout << "\n"; // Print second array std::cout << "Second array contains :"; for (int i = 0; i < n; i++) std::cout << " " << second[i]; std::cout << "\n\n"; std::vector<int> v(10); std::vector<int>::iterator it, st; // Sorting both the arrays std::sort(first, first + 5); std::sort(second, second + 5); // Using default operator< it = std::set_symmetric_difference(first, first + 5, second, second + 5, v.begin(), comp); std::cout << "The symmetric difference has " << (it - v.begin()) << " elements:\n"; for (st = v.begin(); st != it; ++st) std::cout << ' ' << *st; std::cout << '\n'; return 0; }

Output:

First array contains : 5 10 15 20 25 Second array contains : 50 40 30 20 10 The symmetric difference has 6 elements: 5 15 25 30 40 50

**Possible Application :**It is used to find the elements that are present in one container and not in other container.

1. It is used to find the **list of students that are not taking both classes.** Students of both classes are present in lists.

// CPP program to illustrate // std :: set_symmetric_difference #include <iostream> // std::cout #include <algorithm> // std::set_symmetric_difference, std::sort #include <vector> // std::vector // Custom function bool comp(int a, int b) { return a < b; } // Driver code int main() { int first[] = { 5, 10, 15, 20, 25 }; int second[] = { 50, 40, 30, 20, 10 }; int n = sizeof(first) / sizeof(first[0]); // Print first array std::cout << "First array contains :"; for (int i = 0; i < n; i++) std::cout << " " << first[i]; std::cout << "\n"; // Print second array std::cout << "Second array contains :"; for (int i = 0; i < n; i++) std::cout << " " << second[i]; std::cout << "\n\n"; std::vector<int> v(10); std::vector<int>::iterator it, st; // Sorting both the arrays std::sort(first, first + 5); std::sort(second, second + 5); // Using default operator< it = std::set_symmetric_difference(first, first + 5, second, second + 5, v.begin(), comp); std::cout << "The symmetric difference has " << (it - v.begin()) << " elements:\n"; for (st = v.begin(); st != it; ++st) std::cout << ' ' << *st; std::cout << '\n'; return 0; }

OUTPUT :

Students in first batch : Rohan Rajesh Sachin Rahul Abhishek Students in second batch : Rohit Mohak Rishabh Rajesh Abhishek Students attending both batches are : Mohak Rahul Rishabh Rohan Rohit Sachin

2. It can also be use to **find the numbers from both list that are not present in both list.**

Program is given above.

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