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C++ std operator!=C++ std operator!= is a non-member overloaded function of set. This function is used to check whether the two sets are equal or not. Note: Comparison between set objects is based on a pair wise comparison of the elements. Two sets are equal if they have the same number of elements and their corresponding elements have the same values. Otherwise they are not equal.Syntaxtemplate <class T, class Compare, class Alloc> bool operator!= ( const set<T,Compare,Alloc>& lhs, const set<T,Compare,Alloc>& rhs ); Parameterlhs: First set object. rhs: Second set object. Return valueIt returns true if the left side of the set object is equal to the right side of the set object otherwise false. ComplexityComplexity will be constant, if the size of lhs and rhs is different. Otherwise, up to linear in the size of lhs and rhs. Iterator validityNo changes. Data RacesContainers, lhs and rhs are accessed. Concurrently accessing the elements of unmodified set is always safe. Exception SafetyThis function does not throw an exception. Example 1Let's see the simple example to check whether the two sets are equal or not: #include <iostream> #include <set> using namespace std; int main(void) { set<char> m1; set<char> m2; m1.emplace('a'); if (m1 != m2) cout << "Both sets are not equal." << endl; m1 = m2; if (!(m1 != m2)) cout << "Both sets are equal." << endl; return 0; } Output: Both sets are not equal. Both sets are equal. In the above example, there are two sets m1 and m2. m1 contains one element and m2 is empty. When we compare both sets then it will display the message "both sets are not equal" and after assigning m1 to m2 both sets have equal element then it will display the message that "both sets are equal". Example 2Let's see a simple example: #include <set> #include <iostream> int main () { using namespace std; set <int> m1, m2, m3; int i; for (i = 0; i <3; i ++) { m1.insert (i); m2.insert (i * i); m3.insert (i); } if (m1!= m2) cout << "The sets m1 and m2 are not equal." << endl; else cout << "The sets m1 and m2 are equal." << endl; if (m1!= m3) cout << "The sets m1 and m3 are not equal." << endl; else cout << "The sets m1 and m3 are equal." << endl; return 0; } Output: The sets m1 and m2 are not equal. The sets m1 and m3 are equal. Example 3Let's see a simple example: #include <iostream> #include <set> using namespace std; int main () { set < int > s1 , s2 ; s1 . insert ( 10 ); s1 . insert ( 20 ); s1 . insert ( 30 ); s2 = s1 ; cout << ( s1 != s2 ) << endl ; s2 . insert ( 40 ); cout << ( s1 != s2 ) << endl ; } Output: 0 1 In the above example if set s1 and s2 are equal then it will return 1 otherwise 0. Example 4#include <set> #include <iostream> using namespace std; int main () { set<string> m2; typedef set<string> login; m2 = {"xyz@123"} ; //stored password string password; login m1; cout<<"---------Login----------"<<endl<<endl; cout<<"Enter password: \n"; cin>> password; // Get value m1.insert( password ); // Put them in set cout<<"Password you have entered: \n"; for (auto it = m1.begin(); it != m1.end(); it++) { cout << (*it)<< endl; } cout<<"Password stored in the system :\n"; for (auto it = m2.begin(); it != m2.end(); it++) { cout << (*it)<< endl; } if (m1 != m2) cout << "\nIncorrect Password..." << endl; else cout << "\nWelcome to your Page..." << endl; return 0; } Output: 1). ---------Login---------- Enter password: xyz Password you have entered: xyz Password stored in the system: [email protected] Incorrect Password... 2). ---------Login---------- Enter password: [email protected] Password you have entered: [email protected] Password stored in the system: [email protected] Welcome to your Page... In the above example, there are two sets m1 and m2. m1 contains stored password and second set m2 stores user's entered password. It checks whether the both set has same elements or not. If password will match then login is successful otherwise login fails.
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