Isomorphic Strings

题目：

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to gett.

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.

分析：使用字母对照表

代码：

class Solution {public:    bool isIsomorphic(string s, string t) {        int lengths=s.length();        char stable[1000];        char ttable[1000];        for(int i=0; i<1000; i++)        {            stable[i]=-1;        }         for(int i=0; i<1000; i++)        {            ttable[i]=-1;        }        for(int i=0; i<lengths; i++)        {            if((stable[s[i]-' ']==-1)&&(ttable[t[i]-' ']==-1))            {                 stable[s[i]-' ']=t[i];                 ttable[t[i]-' ']=s[i];                 continue;            }            if((stable[s[i]-' ']==t[i]))            {                continue;            }            return false;        }        return true;            }};