【Leetcode】Isomorphic Strings

题目链接：https://leetcode.com/problems/isomorphic-strings/

题目：

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.

思路：

用HashMap存储字符之间映射关系，要注意是双向映射即a映射到b，b也要映射到a，用hashmap要判断两次。

算法：

[java] view plain copy

 

1. public boolean isIsomorphic(String s, String t) {  
2.     char strs[] = s.toCharArray();  
3.     char patterns[] = t.toCharArray();  
4.     Map<Character, Character> maps = new HashMap<Character, Character>();  
5.   
6.     for (int i = 0; i < strs.length; i++) {  
7.         if (maps.containsKey(strs[i])) {  
8.             if (!(maps.get(strs[i]).charValue() == patterns[i])) {  
9.                 return false;  
10.             }  
11.         } else {  
12.             maps.put(strs[i], patterns[i]);  
13.         }  
14.     }  
15.   
16.     maps.clear();  
17.     for (int i = 0; i < patterns.length; i++) {  
18.         if (maps.containsKey(patterns[i])) {  
19.             if (!(maps.get(patterns[i]).charValue() == strs[i])) {  
20.                 return false;  
21.             }  
22.         } else {  
23.             maps.put(patterns[i], strs[i]);  
24.         }  
25.     }  
26.     return true;  
27. }