n-queens

问题 I have some difficulty in understanding the Scala solution to the n Queens problem, below is the implementation assuming isSafe is defined correctly def queens(n: Int): Set[List[Int]] = { def placeQueens(k: Int): Set[List[Int]] = k match { case 0 => Set(List()) case _ => for { queens <- placeQueens(k - 1) col <- 0 until n if isSafe(col, queens ) }yield k :: queens } placeQueens(n) } The for comprehension, as I have seen, theoretically should return a buffered collection, and I see here it

问题 I'm studying the n-queen backtracker. Can someone explain to me how other_row_pos checks for diagonals? I'm not sure why it works or how it works. taken from wikibooks - http://en.wikibooks.org/wiki/Algorithm_Implementation/Miscellaneous/N-Queens: bool isSafe(int queen_number, int row_position) { // Check each queen before this one for(int i=0; i<queen_number; i++) { // Get another queen's row_position int other_row_pos = position[i]; // Now check if they're in the same row or diagonals if

问题 def queens(n: Int): List[List[(Int, Int)]] = { def placeQueens(k: Int): List[List[(Int, Int)]] = if (k == 0) List(List()) else for { queens <- placeQueens(k - 1) column <- 1 to n queen = (k, column) if isSafe(queen, queens) } yield queen :: queens placeQueens(n) } I don't understand how this code works, even tough I debugged in Eclipse. Can you explain step by step this code? By the way, code works correctly. I also understand the n-queens algorithm but I don't understand the mechanism of

问题 I am working a problem that seems to be somewhat famous among beginning programmers, the 8 queens puzzle. I have seen several solutions to this problems using 2D arrays, recursion etc, but this problem is an assignment given in CS course book chapter introducing 1D arrays, so the available techniques to solve this problem are limited. The procedure I have used, is by first creating a 1D array with the size of 64, which makes possible positions to place queens from index 0 to 63. A random

问题 I have some code here that solves the n queens problem using backtracking in python. When I run it, the odds always take much less time than the evens. This is especially evident when the n gets to around 20+. Does anyone know why this is? import time global N N = int(input("Enter N: ")) def display_solution(board): print('\n'.join(['\t'.join([str(cell) for cell in row]) for row in board])) def safe(board, row, col): for i in range(col): if board[row][i] == 1: return False for i, j in zip

问题 I have some code here that solves the n queens problem using backtracking in python. When I run it, the odds always take much less time than the evens. This is especially evident when the n gets to around 20+. Does anyone know why this is? import time global N N = int(input("Enter N: ")) def display_solution(board): print('\n'.join(['\t'.join([str(cell) for cell in row]) for row in board])) def safe(board, row, col): for i in range(col): if board[row][i] == 1: return False for i, j in zip

问题 I am quite confused with idea of implementing 8-queen problem using dynamic programming. It seems it is not possible at one end as for DP " if the problem was broken up into a series of subproblems and the optimal solution for each subproblem was found, then the resulting solution would be realized through the solution to these subproblems. A problem that does not have this structure cannot be solved with dynamic programming" (Reference). By taking this in account, the optimal solution for

问题 How can i go about implemting 8/4 queens problem?Should i use DFS/BFS,I think DFs will be better. Can any one give some pseudocode/guidlines? 回答1: Use a stack and backtracking, easiest way is via recursion. See these other SO posts: Dumb 8 Queens problem in C++ 回答2: My solution have 2 pre-defined logics, there is only one queen at row, and there is only one queen at column. There is an one-dimensional array that length is 8. All array value set one of the 0-7, but all values used exactly one

问题 I am trying to understand N-queens problem's solution as given below: :- use_module(library(clpfd)). n_queens(N, Qs) :- length(Qs, N), Qs ins 1..N, safe_queens(Qs). safe_queens([]). safe_queens([Q|Qs]) :- safe_queens(Qs, Q, 1), safe_queens(Qs). safe_queens([], _, _). safe_queens([Q|Qs], Q0, D0) :- Q0 #\= Q, abs(Q0 - Q) #\= D0, D1 #= D0 + 1, safe_queens(Qs, Q0, D1). I am not able to understand the below snippet: safe_queens([]). safe_queens([Q|Qs]) :- safe_queens(Qs, Q, 1), safe_queens(Qs).

问题 I have just solved the nqueen problem in python. The solution outputs the total number of solutions for placing n queens on an nXn chessboard but trying it with n=15 takes more than an hour to get an answer. Can anyone take a look at the code and give me tips on speeding up this program...... A novice python programmer. #!/usr/bin/env python2.7 ############################################################################## # a script to solve the n queen problem in which n queens are to be