利用python分别采用递归和迭代两种算法解决八皇后问题，

八皇后问题是一个经典的回溯算法问题，其目标是在一个8×8的棋盘上放置8个皇后，使得任意两个皇后都不能处于同一行、同一列或同一斜线上。

递归实现八皇后问题：

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

for solution in queens():
    print(solution)

迭代实现八皇后问题：

def queens(num=8):
    solutions = [(pos,) for pos in range(num)]
    for i in range(num-1):
        solutions = [solution+(pos,)
                     for solution in solutions
                     for pos in range(num)
                     if not conflict(solution, pos)]
    return solutions

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

for solution in queens():
    print(solution)

以上两种算法都可以求出八皇后问题的解，但递归算法更加简洁易懂，而迭代算法则更加直观易懂。