vector<string> wordBreak(string s, unordered_set<string> &dict) {
string result;
vector<string> solutions;
int len = s.size();
vector<bool> possible(len + 1, true);
GetAllSolution(0, s, dict, len, result, solutions, possible);
return solutions;
}
std::vector<std::string> wordBreak2(std::string s, std::unordered_set<std::string>& dict)
{
std::string result;
std::vector<std::string> solutions;
int len = s.size();
std::vector<bool> possible(len, true); //possible[i]为true表示[i, n - 1]有解
GetAllSolution(0, s, dict, len, result, solutions, possible);
return solutions;
}
void GetAllSolution(int start, const string& s, const unordered_set<string> &dict, int len, string& result, vector<string>& solutions, vector<bool>& possible)
{
if (start == len)
{
solutions.push_back(result.substr(0, result.size() - 1)); //eliminate the last space
return;
}
for (int i = start; i < len; ++i)
{
string piece = s.substr(start, i - start + 1);
if (dict.find(piece) != dict.end() && possible[i + 1])
{
result.append(piece).append(" ");
int beforeChange = solutions.size();
GetAllSolution(i + 1, s, dict, len, result, solutions, possible);
if (solutions.size() == beforeChange)
possible[i + 1] = false;
result.resize(result.size() - piece.size() - 1);
}
}
}
void GetAllSolution(int start, const std::string& s, const std::unordered_set<std::string>& dict,
int len, std::string& result, std::vector<std::string>& solutions, std::vector<bool>& possible)
{
if (start == len)
{
solutions.push_back(result.substr(0, result.size() - 1));//去除最后的空格
return;
}
for (int i = start; i < len; ++i)
{
std::string piece = s.substr(start, i - start + 1);
if (dict.find(piece) != dict.end() && possible[i]) // 必须是剩余区间有解才继续递归
{
result.append(piece).append(" ");
int beforeChange = solutions.size();
GetAllSolution(i + 1, s, dict, len, result, solutions, possible);
if (solutions.size() == beforeChange) // 判断剩余区间是否有解
possible[i] = false;
result.resize(result.size() - piece.size() - 1);
}
}
}
