Isomorphic Strings
问题：
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.
思路：
读懂题意后，简单的映射问题而已 Hashmap
我的代码：
public class Solution { public boolean isIsomorphic(String s, String t) { if(s==null && t==null) return true; if(s==null || t==null || s.length()!=t.length()) return false; int len = s.length(); HashMap<Character,Character> oneToTwo = new HashMap<Character,Character>(); HashMap<Character,Character> twoToOne = new HashMap<Character,Character>(); for(int i=0; i<len; i++) { char a = s.charAt(i); char b = t.charAt(i); if(oneToTwo.containsKey(a)) { char tmp = oneToTwo.get(a); if(b != tmp) return false; } else oneToTwo.put(a, b); if(twoToOne.containsKey(b)) { char tmp = twoToOne.get(b); if(a != tmp) return false; } else twoToOne.put(b, a); } return true; } }
他人代码：
public class Solution { public boolean isIsomorphic(String s, String t) { char[] map1 = new char[256], map2 = new char[256]; for (int i = 0; i < s.length(); i++) { char a = s.charAt(i); char b = t.charAt(i); if (!this.map(a, b, map1) || !this.map(b, a, map2)) { return false; } } return true; } private boolean map(char a, char b, char[] map) { if (map[a] == 0) { map[a] = b; } return map[a] == b; } }
学习之处：
对于char类型的hashmap问题，为什么为什么不用数组非得用hashmap呢，下次应该注意常用char数组，而非hashmap
原文：http://www.cnblogs.com/sunshisonghit/p/4479185.html
