"Leetcode" N-queens

N-queens

The n-queens Puzzle is the problem of placing N Queens on a nxn chessboard such that No, Queens attack.

Given an integer n, return all distinct solutions to the n-queens puzzle.

Each solution contains a distinct board configuration of the n-queens ' placement, where ‘Q‘ and ‘.‘ both Indi Cate a queen and an empty space respectively.

For example,
There exist-distinct solutions to the 4-queens puzzle:

[ [". Q.. ",  //solution 1  " ... Q ",  " Q ... ",".  . Q. "], ["]. Q. ",  //Solution 2  " Q ... ",  " ... Q ",  ". Q.. "]

The Q[i] indicates that the position of the Queen placement of line I is illegal: q[i]==q[level]| | ABS (Q[level]-q[i]) ==abs (level-i)

1 classSolution {2  Public:3vector<vector<string> > Solvenqueens (intN) {4        5vector<int> Q (n,-1);6vector<vector<string> >result;7Getqueens (0, n,result,q);8         returnresult;9     }Ten     One     voidPrintqueens (vector<int> &q,vector<vector<string> > &result) A     { -         intn=q.size (); -vector<string>tmp; the         stringstr; -          for(intI=0; i<n;i++) -         { -Str=""; +              for(intj=0; j<n;j++) -             { +                 if(Q[I]==J) str+='Q'; A                 Elsestr+='.'; at             } - tmp.push_back (str); -         } -         - Result.push_back (TMP); -     } in     -     voidGetqueens (intLevelint&n,vector<vector<string> > &result,vector<int> &q) to     { +         if(level==N) -         { the Printqueens (q,result); *             return; $         }Panax Notoginseng         BOOLflag=false; -          for(intI=0; i<n;i++) the         { +q[level]=i; A             if(IsValid (q,level)) the             { +Getqueens (level+1, n,result,q); -             } $q[level]=-1; $         } -     }   -     the     BOOLIsValid (vector<int> &q,int&Level ) -     {Wuyi   the          for(intI=0; i<level;i++) -         { Wu             if(q[i]==q[level]| | ABS (Q[level]-q[i]) ==abs (level-i))return false; -         } About         $         return true; -     } -};

"Leetcode" N-queens