LeetCode 206 - Isomorphic Strings - 题解/Solution

https://leetcode.com/problems/isomorphic-strings/

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/**
* 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 "egg", "add", return true.
*
* Given "foo", "bar", return false.
*
* Given "paper", "title", return true.
*
* Note: You may assume both s and t have the same length.
*
* @author dongyuxi
*
*/
public class Solution {
public boolean isIsomorphic(String s, String t) {
if (null == s && null == t) {
return true;
}
if (null == s || null == t || s.length() != t.length()) {
return false;
}
Map<Character, Character> map = new HashMap<Character, Character>();
Set<Character> set = new HashSet<Character>();
for (int i = 0; i < s.length(); i++) {
if (map.containsKey(s.charAt(i))) {
if (map.get(s.charAt(i)) != t.charAt(i)) {
return false;
}
} else {
if (set.contains(t.charAt(i))) {
return false;
}
map.put(s.charAt(i), t.charAt(i));
set.add(t.charAt(i));
}
}
return true;
}
}


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