#include "s0131_palindrome_partitioning.hpp"

bool isPalindrome(const string &s, int begin, int end) {
  for (int i = begin, j = end; i <= j; ++i, --j) {
    if (s[i] != s[j]) return false;
  }
  return true;
}

/**
 * @brief 回溯
 *
 * @param path 每个元素都是一个回文串
 * @param result 存放最终结果
 * @param s 待处理的字符串
 * @param startIndex s[0...startIndex - 1] 被分成了很多个子字符串，存放在 path 中
 */
void partitionDFS(vector<string> &path, vector<vector<string>> &result, const string &s, int startIndex) {
  int len = s.length();
  // 终止条件
  if (startIndex == len) {
    result.push_back(path);
  }

  for (int i = startIndex; i < len; ++i) {
    // 如果 s[startIndex...i] 是回文串，则进入下一层
    if (isPalindrome(s, startIndex, i)) {
      path.push_back(s.substr(startIndex, i - startIndex + 1));
      partitionDFS(path, result, s, i + 1);
      path.pop_back();
    }
  }
}

vector<vector<string>> S0131::partition(string s) {
  vector<vector<string>> result{};
  vector<string> path{};
  partitionDFS(path, result, s, 0);
  return result;
}