Merge pull request #694 from sriharsha200/my-techdoc

Longest Substring Without Repeating Characters

Author: Saviour1001

Strings/Longest_Substring_Without_Repeating_Characters.cpp

@@ -0,0 +1,37 @@
+/*  Longest substring without repeating characters 
+    Given a string s, find the length of the longest substring without repeating characters. 
+    Solution is to use sliding window concept */
+#include<bits/stdc++.h>
+using namespace std;
+    int lengthOfLongestSubstring(string s) {  // Function to implement length Of Longest Substring
+        int i=0,j=0,f=1,ans=0;
+        unordered_map<int,int>m;
+        while(j<s.length()){
+            auto it=m.find(s[j]);
+            if(it==m.end()){
+                m.insert(pair<int,int>(s[j],1)); //  insert new characters in the map 
+                j+=1;
+            }
+            else{
+                if(f==1){  
+                m[s[j]]+=1; // As a sliding window increase frequency of the character 
+                }
+                if(m[s[j]]>1){ // If frequency is grater then 1 move starting point of window 
+                    m[s[i]]-=1; 
+                    i+=1;
+                    f=0;
+                }
+                else{
+                    j+=1; // Move ending point of window
+                    f=1;
+                }
+            }
+            ans=max(ans,j-i); 
+        }
+            return ans;
+    }
+int main(){
+    string s;
+    cin>>s;
+    cout<<lengthOfLongestSubstring(s);
+}