Leetcode:205. Isomorphic Strings(JAVA)

【问题描述】

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.
【思路】

保存一个hashmap，保存映射关系

同时维护一个set，保证一个character不能被同时映射到两个字符上。

【code】

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

HashMap<Character, Character> map = new HashMap<Character, Character>();
Set<Character> set = new HashSet<Character>();

for (int i = 0; i < s.length(); i++) {
char sc = s.charAt(i);
char tc = t.charAt(i);

if (map.containsKey(sc)) {
if (map.get(sc) == tc) {
continue;
} else {
return false;
}
}else {
if (set.contains(tc)) {
return false;
}else {
map.put(sc, tc);
set.add(tc);
}
}
}
return true;
}
}