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.

s思路： 1. isomorphic表示同質(zhì)，對(duì)string來(lái)說(shuō)，就是結(jié)構(gòu)相同，里面的字母是誰(shuí)不重要，比如：abb和cdd就是isomorphic,因?yàn)樾问缴鲜且粯拥摹Ｈ绾闻袛嗄兀?2. 略微思考，有點(diǎn)沒(méi)有眉目，開(kāi)始有點(diǎn)細(xì)微的緊張。不過(guò)還好，做得多了，有底氣了，和這些情緒都相處得很好。回到正題，兩個(gè)string同時(shí)遍歷，例如：”paper”, “title”，把p映射成t,a映射成i,第二次遇到p時(shí)，就查詢之前p映射的是多少，和現(xiàn)在打算映射的值是否一致。如果能通過(guò)所有一致性檢查，說(shuō)明就是isomorphic的；中間任何地方不一致，就不是！ 3. 代碼第一次寫(xiě)的時(shí)候，默認(rèn)只用一個(gè)unordered_map來(lái)存s[i]->t[i]的映射，但是對(duì)”agg”和”ggg”則不正確了，還需要存t[i]->s[i]的映射，因?yàn)橹挥羞@個(gè)映射，a和g映射成g都是合法的，但題目要求，不允許兩個(gè)字母映射成一個(gè)字母。因此需要兩個(gè)map來(lái)保存相互的映射關(guān)系最保險(xiǎn)！