Merge pull request #477 from nidhisethi88/master

Added solution to leetcode 3 in cpp

Author: Saviour1001

Strings/length_of_longest_substring_without_repeat_char.cpp

@@ -0,0 +1,19 @@
+int lengthOfLongestSubstring(string s) {
+        if(s.length()<=1)
+            return s.length();
+        vector<int> freq(128,0);
+        int si=0,ei=0,n=s.length(),maxlen=INT_MIN,count=0;
+        while(ei<n){
+            if(freq[s[ei++]]++ > 0)
+                count++;
+            
+            while(count>0){                 //if freq of char at ei in the chosen substring is greater than 2
+                if(freq[s[si++]]-- >1)    //iterate till the freq becomes 1
+                    count--;
+            }
+            
+            if(ei-si>maxlen)                //each time compare length of obtained substr with unique char to the maximum length
+                maxlen=ei-si;
+        }
+        return maxlen;
+    }