(java) Isomorphic Strings

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:将匹配规则记录在一个map中，如果这个规则map中没有，则将这个规则加入到这个map中，逐步建立一个字典，如果有，按照字典中的匹配规格匹配，看匹配到的和想要的是否相同就可。

代码如下(已通过leetcode)

public class Solution {

public boolean isIsomorphic(String s, String t) {

Map map = new HashMap();

for (int i = 0; i < s.length(); i++) {

if (map.get(s.charAt(i)) == null) {

if(map.containsValue(t.charAt(i))) return false;

else map.put(s.charAt(i), t.charAt(i));

} else {

if((char)map.get(s.charAt(i))!=t.charAt(i)) return false;

}

}

return true;

}

}