Isomorphic Strings

1 题目描述

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.
题目出处：https://leetcode.com/problems/isomorphic-strings/

2 解题思路

1.使用hashmap来解决，通过比较

3 源代码

package com.larry.easy;

import java.util.HashMap;

public class IsomorphicStrings {
public boolean isIsomorphic(String s, String t) {
if(s.length() != t.length()) return false;

boolean retn = true;
HashMap<Character, Character> hm = new HashMap<Character, Character>();
for(int i = 0; i < s.length(); i++){
char fir = s.charAt(i);
char secd = t.charAt(i);

boolean retn1 = hm.containsKey(fir);//该字符在s中是否出现过
if(retn1){//出现过
char temp = hm.get(fir);
if(temp == secd) continue;
else {
retn = false;
break;
}
}else{//没出现过
boolean retn2 = hm.containsValue(secd);
if(retn2){
retn = false;
break;
}else {
hm.put(fir, secd);
continue;
}
}
}
return retn;
}
public static void main(String[] args) {
/*String s1 = "egg";
String t1 = "add";*/
/*String s1 = "foo";
String t1 = "bar";*/
/*String s1 = "paper";
String t1 = "title";*/
String s1 = "paper";
String t1 = "tttle";
String s = s1;
String t = t1;
IsomorphicStrings is = new IsomorphicStrings();
System.out.println(is.isIsomorphic(s, t));
}
}