实现壹个五子棋AI的落子函数,通常需要思考下面内容流程：

1. 判断当前棋盘的情形,确定最佳落子位置。
2. 实现评估函数,评估棋盘上各种也许的落子点。
3. 根据评估函数的结局选择最佳落子点。

下面内容一个简单的五子棋AI落子函数的Python示例,运用极简的评估函数和随机选择落子点的策略：

import random
# 棋盘大致
BOARD_SIZE = 15
# 初始化棋盘
def init_board():
    return [['.' for _ in range(BOARD_SIZE)] for _ in range(BOARD_SIZE)]
# 检查是否五子连珠
def check_five_in_a_row(board, x, y, player):
    directions = [(0, 1), (1, 0), (1, 1), (1, -1)]
    for dx, dy in directions:
        count = 1
        for d in [-1, 1]:
            nx, ny = x + dx * d, y + dy * d
            if 0 <= nx < BOARD_SIZE and 0 <= ny < BOARD_SIZE and board[nx][ny] == player:
                count += 1
                if count == 5:
                    return True
    return False
# 评估函数
def evaluate(board, x, y, player):
    if check_five_in_a_row(board, x, y, player):
        return float('inf')
    if check_five_in_a_row(board, x, y, player.swapcase()):
        return float('-inf')
    return 0
# 随机选择落子点
def random_move(board, player):
    while True:
        x = random.randint(0, BOARD_SIZE - 1)
        y = random.randint(0, BOARD_SIZE - 1)
        if board[x][y] == '.':
            return x, y
# AI落子函数
def ai_move(board, player):
    best_score = float('-inf')
    best_move = None
    for x in range(BOARD_SIZE):
        for y in range(BOARD_SIZE):
            if board[x][y] == '.':
                board[x][y] = player
                score = evaluate(board, x, y, player)
                board[x][y] = '.'
                if score > best_score:
                    best_score = score
                    best_move = (x, y)
    return best_move
# 主函数
def main():
    board = init_board()
    player = 'X'  # AI玩家为X
    while True:
        if player == 'X':
            move = ai_move(board, player)
            board[move[0]][move[1]] = player
            print("AI moves to ({}, {})".format(move[0], move[1]))
        else:
            # 假设玩家是手动输入
            x, y = map(int, input("Player moves to (x y): ").split())
            if 0 <= x < BOARD_SIZE and 0 <= y < BOARD_SIZE and board[x][y] == '.':
                board[x][y] = player
                print("Player moves to ({}, {})".format(x, y))
            else:
                print("Invalid move. Try again.")
                continue
        # 检查是否游戏结束
        if check_five_in_a_row(board, x, y, player):
            print("Player {} wins!".format(player))
            break
        player = player.swapcase()
if __name__ == "__main__":
    main()

这个示例中，AI运用的是极简的评估函数，只检查是否形成五子连珠,壹个更强大的AI会运用更复杂的评估函数来思考更多的策略影响。

这个示例只一个特别基础的AI实现，实际应用中你也许需要更复杂的算法，如Minimax搜索、Alpha-Beta剪枝或者机器进修等。