Leetcode #52 N-queens II

Title Link: https://leetcode.com/problems/n-queens-ii/

The bitwise operation of the N queen problem is realized.

1 classSolution2 {3  Public:4     intTotalnqueens (intN)5     {6Upperlimit = (1<< N)-1;//if n is 8, then Upperlimit is "11111111". 7Placequeen (0,0,0);8 9         returncount;Ten     } One  A     voidPlacequeen (intDownintLeftintRight//Down : Just below/left: bottom Right  -     { -         intAvailablebits =0;//A bit of "1" in availablebits, indicating that the position can be placed in the Queen.  the  -         if(down = = Upperlimit)//a "1" is placed underneath all locations, where all positions are placed.  -         { -++count; +         } -         Else +         { A             //The "1" in the Left | Right is the position occupied by the other queens, and the "1" indicates the position of the Queen.  atAvailablebits = upperlimit & (~ | left |Right )); -              while(availablebits) -             { -                 //Remove the rightmost "1" in the availablebits, such as Availablebits = "11110000", and the result is "00010000" -                 //Place the next queen in the "1" position and remove the "1" from the availablebits.  -                 intNextqueen = availablebits & (-availablebits); inAvailablebits-=Nextqueen; -  to                 //recursively call, place the next queen, and consider the effect on the next line: +                 //The status changes to (Down | nextqueen, (left | nextqueen) << 1, (right | nextqueen) >> 1).  -                 //The effect on the left diagonal, corresponding to the lower-left position, and the effect on the right diagonal, corresponds to the lower-right position.  thePlacequeen (Down | nextqueen, (left | nextqueen) <<1, (right | nextqueen) >>1); *             } $         }Panax Notoginseng     } -  the     intUpperlimit =0; +     intCount =0; A};

Leetcode #52 N-queens II