205. Isomorphic Strings
problem description
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.
Example 1:
Input: s = "egg", t = "add"
Output: true
Example 2:
Input: s = "foo", t = "bar"
Output: false
Example 3:
Input: s = "paper", t = "title"
Output: true
Note:
You may assume both s and t have the same length.
algorithm thought
直接用map建立起两个字符串中每个字符之间的映射关系就很好解决
code
class Solution {
public:
bool isIsomorphic(string s, string t) {
unordered_map<char,char> ma;
unordered_set<char> se;
for(int i=0;i<s.size();++i){
if(!ma.count(s[i])){
if(se.count(t[i]))
return false;
ma[s[i]]=t[i];
se.insert(t[i]);
}else{
if(t[i]==ma[s[i]])
continue;
else{
return false;
}
}
}
return true;
}
};
algorithm analysis
一次遍历,时间复杂度O(n),用了map和set保存映射关系,空间复杂度O(n)
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