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

  1. // Isomorphic Strings
  2. // Time Complexity: O(n), Space Complexity: O(n)
  3. public class Solution {
  4.     public boolean isIsomorphic(String s, String t) {
  5.         if (s.length() != t.length()) return false;
  7.         final Map<Character,Character> map1 = new HashMap<>();
  8.         final Map<Character,Character> map2 = new HashMap<>();
  10.         for (int  i = 0; i < s.length(); ++i) {
  11.             final char c1 = s.charAt(i);
  12.             final char c2 = t.charAt(i);
  14.             if (map1.containsKey(c1)) {
  15.                 if (map1.get(c1) != c2) return false;
  16.             } else {
  17.                 map1.put(c1, c2);
  18.             }
  20.             if (map2.containsKey(c2)) {
  21.                 if (map2.get(c2) != c1) return false;
  22.             } else {
  23.                 map2.put(c2, c1);
  24.             }
  25.         }
  26.         return true;
  27.     }
  28. }

相关题目

原文: https://soulmachine.gitbooks.io/algorithm-essentials/content/java/string/isomorphic-strings.html