Isomorphic Strings —— Leetcode

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.

新题，C++跑了9ms，自认为还不错。

思路是定义两个hashtable（两个256数组），h1存放s中对应的t，h2存放对应的t是否出现过；情况有<ab,aa>, <paper, title>几种情况；

另外ASC码表中第一个是NULL，也就是全零，数组初始化时会将所有元素初始化为全零；

int array[5] = {-1};这种情况的结果是{-1, 0, 0, 0, 0}；

下面是代码：

class Solution {
public:
    bool isIsomorphic(string s, string t) {
        char h1[256] = {NULL};
        bool h2[256] = {false};
        for(int i=0; i<s.size(); i++)
        {
            if(h1[s[i]] != NULL)
            {
                if(h1[s[i]] != t[i])
                    return false;
            }
            else
            {
                if(h2[t[i]]==1)
                    return false;
                h1[s[i]] = t[i];
                h2[t[i]] = 1;
            }
        }
        return true;
    }
};