Word Pattern in C++

Suppose we have a pattern and a string str, find if str follows the same pattern. Here follow means there is a bijection between a letter in pattern and a non-empty word in str.

So, if the input is like pattern = "cbbc", str = "word pattern pattern word", then the output will be True.

To solve this, we will follow these steps −

• strcin := str

• Define an array of words

• for each word in strcin

  • insert word at the end of words

• Define one map p2i

• i := 0

• pat := empty string

• for c in pattern −

  • if c is not member of p2i, then −

    • (increase i by 1)

    • p2i[c] := i

  • pat := pat concatenate p2i[c]

• Define one map str2i

• i := 0

• pat1 := blank string

• for c in words −

  • if c is not member of str2i, then −

    • (increase i by 1)

    • str2i[c] := i

  • pat1 := pat1 concatenate str2i[c]

• return true when pat1 is same as pat

Example 

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   bool wordPattern( string pattern, string str ) {
      istringstream strcin(str);
      string word;
      vector<string> words;
      while (strcin >> word)
         words.push_back(word);
      unordered_map<char, int> p2i;
      int i = 0;
      string pat = "";
      for (auto c : pattern) {
         if (p2i.count(c) == 0) {
            i++;
            p2i[c] = i;
         }
         pat += to_string(p2i[c]);
      }
      unordered_map<string, int> str2i;
      i = 0;
      string pat1 = "";
      for (auto c : words) {
         if (str2i.count(c) == 0) {
            i++;
            str2i[c] = i;
         }
         pat1 += to_string(str2i[c]);
      }
      return pat1 == pat;
   }
};
main(){
   Solution ob;
   cout << (ob.wordPattern("cbbc", "word pattern pattern word"));
}

Input

"cbbc", "word pattern pattern word"

Output

1