Python列表和字典是否被覆盖或损坏？

问题描述

我正试图用蛮力解决N皇后棋问题https://en.wikipedia.org/wiki/Eight_queens_puzzle

我的代码正在运行，但是当我尝试返回解决方案数据结构时，会出现异常行为。

包含解决方案的列表有时会被覆盖或损坏。

我尝试使用多个不同的数据结构列表，字典，集合，并且都具有相同的结果。

输出应为

[[1,3,2],[1,2]]

但目前返回为

[[3,3],[3,3]]

import numpy as np

# Validation Functions
def checkRows(state):
    """
    Check only 1 queen per row
    """     
    for row in state:        
        if sum(row) > 1:
            return False
    return True

def checkCols(state):
    """
    Check only 1 queen exists in a column
    """
    for i in range(0,len(state)):
        count = 0
        for j in range(0,len(state)):            
            #print(state[j][i])
            count = count + state[j][i]
        if count > 1: return False
    return True   
    
def checkDiag(state):
    """
    Checks only 1 queen exists per diagonal
    https://stackoverflow.com/questions/6313308/get-all-the-diagonals-in-a-matrix-list-of-lists-in-python
    """
    # Alter dimensions as needed
    n = len(state)
    x,y = n,n
    # incoming state list    
    a = np.array(state)
    diags = [a[::-1,:].diagonal(i) for i in range(-a.shape[0]+1,a.shape[1])]    
    diags.extend(a.diagonal(i) for i in range(a.shape[1]-1,-a.shape[0],-1))
    for n in diags:
        if sum(n) > 1: #if any of the diagonals sums to more than 1 there must be more than 1 queen in that diagonal
            return False
    return True
        
def checkState(state):
    """
    Returns false on one or more failures
    """
    return checkRows(state) and checkCols(state) and checkDiag(state)
    
def worker_translate(dim,sol):
    """
    Translate from the permutations function to a format to be checked by validation functions
    """
    state = []
    for val in range(dim - 1,-1,-1):
        inner_list = []
        for y in sol:            
            if y == val:
                inner_list.append(1)                                
            else:
                inner_list.append(0)  
        state.append(inner_list)
    return state

def print_solution(dim,sol):
    for val in range(dim - 1,-1):
        for y in sol:
            if y == val:
                print('Q ',end='')
            else:
                print('. ',end='')
        print()
    print()


def runner(x):
    # go through the permutations searching for all possible solutions
    dim = int(x)    
    
    # populate this_permutation
    this_permutation = []
    for n in range(dim):
        this_permutation.append(0)

    # calculate the number of permutations
    possible_permutations = dim**dim
#     for n in range(dim):
#         possible_permutations *= dim
        
    mydict = {}
    mylist = []
    # iterate through all possible permutations    
    for n in range(possible_permutations):
        rem = n
        for m in range(dim):
            this_permutation[m] = rem % dim
            rem //= dim

            res = checkState(worker_translate(dim,this_permutation))
            if res:
                #print("Solution Found")
                #print(this_permutation)
                #print(worker_translate(dim,this_permutation))
                #print_solution(dim,this_permutation)
                mylist.append(this_permutation)
                mydict[n] = this_permutation
                print(mydict)
                print(mylist)
    print("data structures not working after this point")
    print(mydict)
    print(mylist)
    return(mydict,mylist)

print(runner(4))
                

已编译代码的输出

{114: [2,1]}
[[2,1]]
{114: [2,1],[2,1]]
{114: [1,141: [1,2]}
[[1,2]]
{114: [1,2]]
data structures not working after this point
{114: [3,141: [3,3]}
[[3,3]]
({114: [3,3]},[[3,3]])

Process finished with exit code 0

解决方法

请参阅注释中的Collin Heist答案以获取解释。

mylist.append(this_permutation.copy())