[leetcode]205. Isomorphic Strings同构字符串

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

题意：

给定字符串s和t，判断能否通过字符间的一一对应关系，把前者变成后者。

思路：

既然是一一对应，用两个HashMap来解决

这里用char [] mapAB = new char[256] 作为简化版的HashMap

代码：

 1 class Solution {
 2     public boolean isIsomorphic(String s, String t) {
 3         if(s.length()!=t.length()) return false;     
 4          char [] mapAB = new char[256];
 5          char [] mapBA = new char[256];
 6          for(int i = 0; i<s.length();i++){
 7             char a = s.charAt(i);
 8             char b = t.charAt(i);    
 9             if(mapAB[a]!=0){
10                 if(mapAB[a]!=b) return false;
11             }else{
12                 mapAB[a]= b;
13             } 
14             if(mapBA[b]!=0){
15                 if(mapBA[b]!=a) return false;
16             }else{
17                 mapBA[b]=a;
18             }           
19         } 
20         return true;   
21     }
22 }