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.

题解：显然是哈希查找，但是其实没必要用map，一共就255个字符，每次只记录它现在的位置就好（因为之前的位置都比较过了）。

class Solution {public:    bool isIsomorphic(string s, string t) {        int hs[256]={
   0};        int ht[256]={
   0};        int ls=s.length(),lt=t.length();        if(ls!=lt) return false;        for(int i=0;i