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
Note:
You may assume both s and t have the same length.
Solution
Using HashMap
class Solution {
public boolean isIsomorphic(String s, String t) {
if (s.length() != t.length()) return false;
Map<Character, Character> map = new HashMap<>();
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 (map.containsValue(t.charAt(i))) return false;
map.put(s.charAt(i), t.charAt(i));
}
}
return true;
}
}
Using Array to replace Map
class Solution {
public boolean isIsomorphic(String s, String t) {
int[] stmap = new int[256];
int[] tsmap = new int[256];
Arrays.fill(stmap, -1);
Arrays.fill(tsmap, -1);
for (int i = 0; i < s.length(); i++) {
if (stmap[s.charAt(i)] != tsmap[t.charAt(i)]) return false;
stmap[s.charAt(i)] = i;
tsmap[t.charAt(i)] = i;
}
return true;
}
}
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