Isomorphic Strings
描述
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.
分析
用两个 HashMap 维护字符的映射关系，时间复杂度O(n)，空间复杂度O(n)。
代码
// Isomorphic Strings
// Time Complexity: O(n), Space Complexity: O(n)
public class Solution {
public boolean isIsomorphic(String s, String t) {
if (s.length() != t.length()) return false;
final Map<Character,Character> map1 = new HashMap<>();
final Map<Character,Character> map2 = new HashMap<>();
for (int i = 0; i < s.length(); ++i) {
final char c1 = s.charAt(i);
final char c2 = t.charAt(i);
if (map1.containsKey(c1)) {
if (map1.get(c1) != c2) return false;
} else {
map1.put(c1, c2);
}
if (map2.containsKey(c2)) {
if (map2.get(c2) != c1) return false;
} else {
map2.put(c2, c1);
}
}
return true;
}
}