131.cpp

// dp-dfs.cpp
class Solution {
    void dfs(int index, string& s, vector<string>& path,
             vector<vector<string>>& ret, vector<vector<bool>>& dp) {
        if (index == s.size()) {
            ret.push_back(path);
            return;
        }
        for (int i = index; i < s.size(); ++i)
            if (dp[index][i]) {
                path.push_back(s.substr(index, i - index + 1));
                dfs(i + 1, s, path, ret, dp);
                path.pop_back();
            }
    }

  public:
    vector<vector<string>> partition(string s) {
        int n = s.size();
        if (n == 0)
            return {};
        vector<vector<string>> ret;
        vector<string> path;
        vector<vector<bool>> dp(n, vector<bool>(n, 0));
        for (int i = 0; i < n; ++i)
            for (int j = 0; j <= i; ++j)
                dp[j][i] = s[i] == s[j] && (i - j <= 2 || dp[j + 1][i - 1]);
        dfs(0, s, path, ret, dp);
        return ret;
    }
};
// dfs.cpp
class Solution2 {
    void dfs(int index, string& s, vector<string>& path,
             vector<vector<string>>& ret) {
        if (index == s.size()) {
            ret.push_back(path);
            return;
        }
        for (int i = index; i < s.size(); ++i)
            if (isPalindrome(s, index, i)) {
                path.push_back(s.substr(index, i - index + 1));
                dfs(i + 1, s, path, ret);
                path.pop_back();
            }
    }
    bool isPalindrome(const string& s, int start, int end) {
        while (start < end)
            if (s[start++] != s[end--])
                return false;
        return true;
    }

  public:
    vector<vector<string>> partition(string s) {
        vector<vector<string>> ret;
        if (s.empty())
            return ret;
        vector<string> path;
        dfs(0, s, path, ret);
        return ret;
    }
};