Merge pull request #3 from adityyyy/adityyyy-patch-3

Create seIterators.cpp

Author: adityyyy

CPP/set & pair/seIterators.cpp

@@ -0,0 +1,37 @@
+#include<bits/stdc++.h>
+using namespace std;
+int main(){
+
+//Set iterators offer less features than vectorr iterators.
+//auto it = s.begin(); //it is the iterator to the first element
+// it++, it--, ++it, --it ->These are all valid and wor in O(log N) time
+
+//NOTE: (it+5) or it+=2 etc are invalid. to advance multiple steps, do it++ multiple times.
+
+//elements of iteratir are always in sorted manner
+set<int> s;
+s.insert(4);
+s.insert(1);
+s.insert(10);
+s.insert(2);
+
+cout<<*s.begin()<<endl;
+
+s.erase(s.begin());
+cout<<*s.begin()<<endl;
+
+/* FUNCTIONS RELATED TO SET ITERATORS:
+    s.find(x): returns iterator to element with value x. Returns s.end() if not found. O(log N)
+
+    s.lower_bound(x): returns iterator to the first element which is >=x. Returns s.end() if not found. O(log N)
+
+    s.upperbound(x): returns iterator to the first element which is >x. Returns s.end() if not found. O(log N)
+
+    s.erase(it): erases the element with iterator it. O(log N)
+
+following 2 lines are same
+it(s.find(10)==s.end()) cout<<"Not found";
+it(s.count(10)==0) cout<<"Not found";
+*/
+    return 0;
+}