# 205. 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.
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
Note:
You may assume both s and t have the same length.
# Solution
Approach 1: Hash table: char -> char or char -> position.
# Code (Python)
Approach 1:
# Code (C++)
Approach 1:
class Solution {
public:
bool isIsomorphic(string s, string t) {
if (s.size() != t.size()) return false;
unordered_map<char,char> stMap;
unordered_map<char,char> tsMap;
for (int i = 0; i < s.size(); ++i)
{
if ((stMap.find(s[i]) != stMap.end() && stMap[s[i]] != t[i]) ||
(tsMap.find(t[i]) != tsMap.end() && tsMap[t[i]] != s[i]))
return false;
stMap[s[i]] = t[i];
tsMap[t[i]] = s[i];
}
return true;
}
};
class Solution {
public:
bool isIsomorphic(string s, string t) {
if (s.size() != t.size()) return false;
int stMap[256] = {0};
int tsMap[256] = {0};
for (int i = 0; i < s.size(); ++i)
{
if (stMap[s[i]] != tsMap[t[i]])
return false;
stMap[s[i]] = i + 1; // the default is 0.
tsMap[t[i]] = i + 1;
}
return true;
}
};