LeetCode OJ Isomorphic Strings

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.

bool isIsomorphic(char* s, char* t) {
	int letter1[256] = { 0 };
	for (int i = 0; s[i] != '\0'; i++) {
		if (!letter1[s[i]]) letter1[s[i]] = t[i];
		else if (letter1[s[i]] != t[i]) return false;
	}
	int letter2[256] = { 0 };
	for (int i = 0; t[i] != '\0'; i++) {
		if (!letter2[t[i]]) letter2[t[i]] = s[i];
		else if (letter2[t[i]] != s[i]) return false;
	}
	return true;
}