class Solution { private: string build(string& str, int i, int j, vector<vector<int>>& directions){ if(i < 1 || j < 1){ return ""; } string ans; if(directions[i][j] == 1){ // 来自左上方 ans += build(str, i - 1, j - 1, directions); ans += str[i-1]; }else if(directions[i...