LeetCode 291. Word Pattern II

BackTracking.

#include <string>
#include <vector>
#include <unordered_map>
#include <iostream>
using namespace std;

/*
  Given a pattern and a string str, find if str follows the same pattern.
  Here follow means a full match, such that there is a bijection between a
  letter in pattern and a non-empty substring in str.
  Example:
  1 Pattern: "abab", str = "redblueredblue", should return true;
  2 Pattern: "aaaa", str = "asdasdasdasd" should return true;
  3 Pattern: "aabb", str = "xyzabcxyzabc" should return false;
  Note: You may assume both pattern and str contains only lowercase letters.
*/
bool wordPattern(string pattern, int i, string str, int j, unordered_map<string, int>& st, unordered_map<char, int>& pat) {
  if(i == pattern.size() && j == str.size()) return true;
  if(i == pattern.size() || j == str.size()) return false;
  char c = pattern[i];
  for(int k = 1; k <= str.size() - j; ++k) {
    if(pat[c] == st[str.substr(j, k)]) {
        pat[c]++;
        st[str.substr(j, k)]++;
      if(wordPattern(pattern, i + 1, str, j + k, st, pat)) return true;
        pat[c]--;
        st[str.substr(j, k)]--;
      }
  }
  return false;
}
bool wordPattern(string pattern, string str) {
  unordered_map<string, int> st;
  unordered_map<char, int> pat;
  return wordPattern(pattern, 0, str, 0, st, pat);
}

int main(void) {
  string pattern_0 = "abab";
  string str_0 = "redblueredblue";
  cout << wordPattern(pattern_0, str_0) << endl;

  string pattern_1 = "aaaa";
  string str_1 = "asdasdasdasd";
  cout << wordPattern(pattern_1, str_1) << endl;


  string pattern_2 = "aabb";
  string str_2 = "xyzabcxyzabc";
  cout << wordPattern(pattern_2, str_2) << endl;

  string pattern_3 = "aabb";
  string str_3 = "aabbcc";
  cout << wordPattern(pattern_3, str_3) << endl;
}