leetcode 205 ： Isomorphic Strings

问题描述：

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.

思路：

这道题思路很直接，就是作字符映射，一个字符映射成另一个字符，而且不能有两个不同的字符映射到同一个字符。

代码中用replace数组来存放字符映射表，而have_mapped数组记录某字符是否已经被映射，避免被两个不同的字符映射。

代码：

class Solution {
public:
bool isIsomorphic(string s, string t) {
char replace[150];
bool have_mapped[150];
for(int i = 0; i < 150; i++)
{
replace[i] = 0;
have_mapped[i] = false;  //avoid the situation that two characters map to the same character
}
for(int i = 0; i < s.size();i++)
{
int s_index = s[i] - 0;
int t_index = t[i] - 0;
if(replace[s_index] == 0)
{
if(have_mapped[t_index] == true) return false;  //test if two characters map to the same character

replace[s_index] = t[i];
have_mapped[t_index] = true;
}
else
{
if(replace[s_index] != t[i]) return false;
}
}
return true;

}
};