Two sets are disjoint set when they have no common elements. In other words, if we get the intersection of two sets, then we will get null set.
The method is simple, in this algorithm, two sets are given. We assume that both sets are already sorted, items are compared between two sets. when there is a match, then it is not a disjoint set, when no items are matched, they are disjoint sets.
Input and Output
Input: Two sets: set1: {15, 12, 36, 21, 14} set2: {7, 89, 56, 32} Output: Both sets are disjoint
Algorithm
isDisjoint(set1, set2)
Input: Two sets.
Output: True when both sets are disjoint.
Begin i1 := start of first set i2 := start of second set while i1 in set1 and i2 in set 2, do if set1[i1] < set2[i2], then i1 := i1 + 1 else if set2[i2] < set1[i1], then i2 := i2 + 1 else return false done return true End
Example
#include<iostream> #include<set> using namespace std; bool isDisjoint(set<int> set1, set<int> set2) { set<int>::iterator i1, i2; i1 = set1.begin(); i2 = set2.begin(); //initialize iterators with first element while(i1 != set1.end() && i2 != set2.end()) { //when both set have some elements to check if(*i1 < *i2) i1++; //when item of first set is less than second set else if(*i2 < *i1) i2++; //when item of second set is less than first set else return false; //if items are matched, sets are not disjoint } return true; } int main() { set<int> set1, set2; int n1, n2; cout << "Enter number of elements in set 1: "; cin >>n1; while(n1 != set1.size()) { //duplicate items will be discarded int item; cout << "Enter element: "; cin >> item; set1.insert(item); } cout << "Enter number of elements in set 2: "; cin >>n2; while(n2 != set2.size()) { int item; cout << "Enter element: "; cin >> item; set2.insert(item); } if(isDisjoint(set1, set2)) cout << "Both sets are disjoint"; else cout << "Sets are not disjoint"; }
Output
Enter number of elements in set 1: 5 Enter element: 15 Enter element: 12 Enter element: 36 Enter element: 21 Enter element: 14 Enter number of elements in set 2: 4 Enter element: 7 Enter element: 89 Enter element: 56 Enter element: 32 Both sets are disjoint