Update Longest_Substring_Without_Repeating_Characters.cpp

* Well documented and tested code for sliding window algorithm.

* Thank you.

Author: ashish5kmax

sliding-window/Longest_Substring_Without_Repeating_Characters.cpp

@@ -1,29 +1,23 @@
 /** Leetcode problem 
 * Author : @ashish5kmax (Ashish Kumar Sahoo)
-
 * 3. Longest_Substring_Without_Repeating_Characters
 * Problem link :- https://leetcode.com/problems/longest-substring-without-repeating-characters/description/
-
 * Intiuation :
   Intuition is strightforward and simple, we track the frequencey and as we know we can't use string to track longest substring without repeating characters, as poping a char from front of string is not in O(1) which could be optimized by deque approch.
-
 * Approch :
     1) At first we initialize a unordered_map to track the frequncy and then.
     2) We initialize deque for pushing the characters and if temp > res we update our res deque to temp as we need longest substring here.
     3) And while loop is used to reduce the frequency from front doing i++ and removing charecters from temp deque as we no longer need them.
     4) return res.size() as we only need size not string.
-
 * Time Complexity :
   O(N)
   
 * Space Complexity :
   O(N)
-
 * Examples:-
   testcase1:- s = "abcabcbb", o/p = 3.
   testcase2:- s = "bbbbb", o/p = 1.
   testcase3:- s = "pwwkew", o/p = 3.
-
 * I hope this helps to understand.
 * Thank you!!
 **/
@@ -32,6 +26,9 @@
 #include <iostream> // for input and output read/write.
 #include <unordered_map> // to use it for character frequency.
 #include <deque> // for push and pop operations at O(1) time.
+#include <string> // for taking string as input
+
+using namespace std; // using the namspace standard to reduce the redundent usage of std:: when calling functions (basically reduicng an extra overhead).
 
 class Solution {
 public:
@@ -80,7 +77,7 @@ int main() {
   // object of class Solution created for function call.
   Solution soln;
 
-  
+
   // user inputted string. 
   string s;
   cout<<"Enter the string : "<<endl;