N皇后Python代码仅n=1/5有效，其余无输出问题求助

我编写了两款解决N皇后问题的Python代码，分别采用numpy数组和列表实现。测试0到20的整数后发现：

• numpy数组版本仅当n=1或5时能输出正确结果，其余n值均输出“No Solution”
• 列表实现版本仅支持n=1，n=5也无法输出结果

numpy数组实现代码 #

import numpy as np

def isSafe(arr, row, col, n):
    for ind in range(row):
        if(arr[ind][col] == 1):
            return False
    x = row
    y = col
    while x >= 0 and y >= 0:
        if arr[x][y] == 1:
            return False
        x -= 1
        y -= 1
    x = row
    y = col

    while x >= 0 and y < n:
        if arr[x][y] == 1:
            return False
        x -= 1
        y += 1
    
    return True

def nQueen(arr, row, n):
    if row >= n:
        return True
    for col in range(n):
        if isSafe(arr,row,col,n) == True:
            arr[row][col] = 1
            if nQueen(arr, row+1, n) == True:
                return True
    
    return False

def main():
    n = int(input("Enter the size of board: "))
    arr = np.zeros((n,n)).astype(int)
    if nQueen(arr, 0, n):
        for x in range(n):
            for y in range(n):
                print(arr[x][y], end='\t')
            print("\n")
    else:
        print("No Solution: ")

if __name__ == '__main__':
    main()

列表实现代码 #

import numpy as np

def isSafe(arr, row, col, n):
    for ind in range(row):
        if(arr[ind][col] == 1):
            return False
    x = row
    y = col
    while x >= 0 and y >= 0:
        if arr[x][y] == 1:
            return False
        x -= 1
        y -= 1
    x = row
    y = col

    while x >= 0 and y < n:
        if arr[x][y] == 1:
            return False
        x -= 1
        y += 1
    
    return True

def nQueen(arr, row, n):
    if row >= n:
        return True
    for col in range(n):
        if isSafe(arr,row,col,n) == True:
            arr[row][col] = 1
            if nQueen(arr, row+1, n) == True:
                return True
    
    return False

def main():
    n = int(input("Enter the size of board: "))
    arr = [[0]*n]*n
    if nQueen(arr, 0, n):
        for x in range(n):
            for y in range(n):
                print(arr[x][y], end='\t')
            print("\n")
    else:
        print("No Solution: ")

if __name__ == '__main__':
    main()

内容的提问来源于stack exchange，提问作者CodingHatesU