# Leetcode: Isomorphic Strings II

Isomorphic Strings

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.

For example,

Given "foo", "bar", return false.

Given "paper", "title", return true.

Note:
You may assume both s and t have the same length.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## Basic Ideas:
##             Build 2 dicts
##             From s to t, and from t to s
##             For any new item to compare, make sure it won't viloate any dict
## Complexity: Time O(n), Space O(1). (Keys of dictionary is quite limited)
class Solution(object):
def isIsomorphic(self, s, t):
"""
:type s: str
:type t: str
:rtype: bool
"""
m1, m2 = {}, {}
for i in xrange(len(s)):
ch1, ch2 = s[i], t[i]
# mapping from s to t
if m1.has_key(ch1):
if m1[ch1] != ch2:
return False
else:
m1[ch1] = ch2

# ab -> aa
# mapping from t to s
if m2.has_key(ch2):
if m2[ch2] != ch1:
return False
else:
m2[ch2] = ch1
return True

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