Leetcode: 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.

注意不同的字符不能映射到同一个字符这个条件。

class Solution {
public:
bool isIsomorphic(string s, string t) {
unordered_map<char, char> charMapping;
unordered_set<char> occupied;
for (int i = 0; i < s.size(); ++i) {
auto iter = charMapping.find(s[i]);
if (iter == charMapping.end()) {
if (occupied.find(t[i]) == occupied.end()) {
charMapping.emplace(s[i], t[i]);
occupied.emplace(t[i]);
}
else {
return false;
}
}
else {
if (t[i] != iter->second) {
return false;
}
}
}

return true;
}
};