leetcode_gym/_problems/isomorphicStrings.md

layout, title, last_solved, category, leetcode_url, status

layout	title	last_solved	category	leetcode_url	status
page	Isomorphic Strings	2020-08-04	hashmap	https://leetcode.com/problems/isomorphic-strings	Solved

Problem

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

Solution

{% highlight python %}

def isIsomorphic(self, s: str, t: str) -> bool:

"""
    egg -> 011
    add -> 011
"""
def isohash(word):
    
    mapping = defaultdict(int)  # key=character, value=seqNum
    res = ""
    seqNum = 0   # seqNum is number that was assigned to char, for "egg": e is assigned '1', g is assigned '2'

    """
        mapping[e]=1
        mapping[g]=2
    """
    for c in word:
        if c not in mapping:
            mapping[c] = seqNum         # assign a number to char (keep track of it in hashmap)
            seqNum+=1                   # increment seqNum by 1 for the next character
            res += str(mapping[c])      # add seqNum to res
        else:
            res += str(mapping[c])      # if already assigned, just add to res


    return res


return isohash(s)==isohash(t)

{% endhighlight %}