回溯法实现8皇后问题python

下面是Python实现8皇后问题的回溯法代码：

def is_valid(board, row, col):
    # 检查列是否有冲突
    for i in range(row):
        if board[i] == col:
            return False
    # 检查右上方是否有冲突
    for i, j in zip(range(row-1, -1, -1), range(col+1, len(board))):
        if board[i] == j:
            return False
    # 检查左上方是否有冲突
    for i, j in zip(range(row-1, -1, -1), range(col-1, -1, -1)):
        if board[i] == j:
            return False
    return True

def solve(board, row):
    if row == len(board):
        return True
    for col in range(len(board)):
        if is_valid(board, row, col):
            board[row] = col
            if solve(board, row+1):
                return True
    board[row] = -1
    return False

def print_board(board):
    for row in board:
        line = ""
        for col in range(len(board)):
            if row == col:
                line += "Q "
            else:
                line += ". "
        print(line)
    print()

board = [-1] * 8
solve(board, 0)
print_board(board)

这里使用了`is_valid`函数来判断当前位置是否可用，`solve`函数实现回溯递归，`print_board`函数用于输出结果。