3. Longest Substring Without Repeating Characters.py

class Solution(object):
   def lengthOfLongestSubstring(self, s):
      i =0
      j = 0
      d={}
      ans = 0
      while j < len(s):
         if s[j] not in d or i>d[s[j]]:
            ans = max(ans,(j-i+1))
            d[s[j]] = j
         else:
            i = d[s[j]]+1
            ans = max(ans,(j-i+1))
            j-=1
         #print(ans)
         j+=1
      return ans
ob1 = Solution()
print(ob1.lengthOfLongestSubstring("ABCABCBB"))