使用 Python 约束解析器求解 N-Queens

Question

下面是 N-queens problem using the Python-Constraint Resolver from Labix 的解决方案。有人可以向我解释一下，或者让我参考任何解释此代码最后 3 行含义的网页吗？

此外，我如何使用 AllDifferentConstraint 约束来缩短下面的代码？

from constraint import *

problem = Problem()
size = 8
cols = range(size)
rows = range(size)
problem.addVariables(cols, rows)
for col1 in cols:
    for col2 in cols:
        if col1 < col2:
            problem.addConstraint(lambda row1, row2, col1=col1, col2=col2:
                                    abs(row1-row2) != abs(col1-col2) and
                                    row1 != row2, (col1, col2))

Answer 1

problem.addConstraint(lambda row1, row2, col1=col1, col2=col2:
                        abs(row1-row2) != abs(col1-col2) and
                        row1 != row2, (col1, col2))

这大致相当于：

def constraintFunction (col1, col2):
    def innerFunction (row1, row2):
        return abs(row1 - row2) != abs(col1 - col2) and row1 != row2
    return innerFunction

problem.addConstraint(constraintFunction(col1, col2), (col1, col2))

最后一行相当于：

func = constraintFunction(col1, col2)
problem.addConstraint(func, (col1, col2))

使用 Python 约束解析器求解 N-Queens

Solving N-Queens Using Python constraint Resolver

python

constraint-programming

n-queens