8皇后问题的回溯算法Python

以下是Python中八皇后问题的回溯算法实现：

def conflict(state, nextX):
    nextY = len(state)
    for i in range(nextY):
        if abs(state[i]-nextX) in (0, nextY-i):
            return True
    return False

def queens(num=8, state=()):
    for pos in range(num):
        if not conflict(state, pos):
            if len(state) == num-1:
                yield (pos,)
            else:
                for result in queens(num, state+(pos,)):
                    yield (pos,) + result

def prettyprint(solution):
    def line(pos, length=len(solution)):
        return '. ' * (pos) + '♛ ' + '. '*(length-pos-1)
    for pos in solution:
        print(line(pos))

count = 0
for solution in queens(8):
    count += 1
    print('Solution', count)
    prettyprint(solution)

这段代码中，`conflict`函数用于判断当前位置是否与之前的皇后位置冲突，`queens`函数用于递归求解八皇后问题，`prettyprint`函数用于将结果输出为可读性更好的形式。最后，我们通过循环调用`queens`函数来输出所有的解。