Saturday, July 6, 2019

Leetcode solution 205: Isomorphic Strings

Problem Statement 

Given two strings s and t, determine if they are isomorphic.
Two strings are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.
Example 1:
Input: s = "egg", t = "add"
Output: true
Example 2:
Input: s = "foo", t = "bar"
Output: false
Example 3:
Input: s = "paper", t = "title"
Output: true
You may assume both and have the same length.
Problem link


Video Tutorial

You can find the detailed video tutorial here

Thought Process

A relatively straightforward problem, very similar to Word Pattern. All we have to do is check the one to one mapping from string a to string b, also it needs to maintain a bijection mapping (meaning no two different characters in a should map to the same character in b)

Use bijection mapping

Check character one by one from a and b. If char in a hasn't been seen before, create a one to one mapping between this char in a and the char in b so later if this char in a is seen again, it has to map to b, else we return false. Moreover, need to make sure the char in b is never mapped by a different character.
An explanation int the video


Time Complexity: O(N), N is the length of string a or string b
Space Complexity: O(N), N is the length of string a or string b because the hashmap and set we use


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