Classic Interview 150 Questions P205 Isomorphic Strings

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Timeline

Timeline

2025-11-13

init

Hash table

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Problem:

P205 Isomorphic Strings

https://leetcode.cn/problems/isomorphic-strings/description/?envType=study-plan-v2&envId=top-interview-150

Hash tables represent mappings. Note that to maintain a mapping, you need two hash tables.

#include <string>
#include <vector>
#include <unordered_map>

using std::string;
using std::unordered_map;

class Solution {
    public:
	bool isIsomorphic(string s, string t)
	{
		if (s.size() != t.size()) return false;
		
		int i, n = s.size();
		unordered_map<char, char> s2tmap;
		unordered_map<char, char> t2smap;


		for (i = 0; i < n; i++) {
			if (!s2tmap.count(s[i]) && !t2smap.count(t[i])) {
				s2tmap[s[i]] = t[i];
				t2smap[t[i]] = s[i];
			} else {
				if (s2tmap[s[i]] != t[i] || t2smap[t[i]] != s[i])
					return false;
			}
		}

		return true;
	}
};