Leetcode Isomorphic Strings

標籤：

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.

解題思路：

 isomorphic a 同形的，同構的

此題非常類似 Leetcode Word Pattern .

用HashMap, s 裡是key, t 裡是value. 每次比較，首先檢查是否已有該key, 若有，檢查對應value 是否相等，不等 return false; 若沒有，檢查value 是否已存在map裡，若有，則two characters may map to the same character， return false, 若沒有，put to map.

Java code:

public boolean isIsomorphic(String s, String t) {        if(s.length() != t.length()){            return false;        }        Map<Character, Character> map = new HashMap<Character, Character>();        for(int i = 0; i < t.length(); i++) {            if(map.containsKey(s.charAt(i))){                if(map.get(s.charAt(i)) != t.charAt(i)){                    return false;                }            }else {                if(map.containsValue(t.charAt(i))){                    return false;                }else {                    map.put(s.charAt(i), t.charAt(i));                }            }        }        return true;    }

 

Leetcode Isomorphic Strings