Classic 150 Interview Questions P290 Word Pattern

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Timeline

Timeline

2025-11-13

init

Hash table

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Problem:

P290 Word Pattern

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

Use a hash table to represent the mapping relationship. If a character and a string have not been mapped or have been mapped, map them. If a character has been mapped, then the current string must be the mapped string.

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

using std::string;
using std::unordered_map;
using std::vector;
using std::stringstream;

class Solution {
    public:
	bool wordPattern(string pattern, string s)
	{
		int i, n = pattern.size();
		vector<string> s_vec;		
		stringstream ss(s);
		string curr;

		while (ss >> curr)
			s_vec.push_back(curr);
		
		if (s_vec.size() != n) return false;

		unordered_map<char, string> p2smap;
		unordered_map<string, char> s2pmap;

		for (i = 0; i < n; i++) {
			if (!p2smap.count(pattern[i]) && !s2pmap.count(s_vec[i])) {
				p2smap[pattern[i]] = s_vec[i];
				s2pmap[s_vec[i]] = pattern[i];
			} else {
				if (p2smap[pattern[i]] != s_vec[i] || s2pmap[s_vec[i]] != pattern[i])
					return false;
			}
		}
		return true;
	}
};