Python栈的应用：卡特兰数的计算

# 计算卡特兰数
def catalan(n):
    stack = []
    # 将h(0)放入栈中
    stack.append(1)
    # 从h(1)开始循环计算
    for i in range(1, n + 1):
        # 计算h(i)
        h_i = 0
        for j in range(i):
            h_i += stack[j] * stack[i - j - 1]
        # 将h(i)放入栈顶
        stack.append(h_i)
    return stack[n]

# 测试
print(catalan(0))  # 1
print(catalan(1))  # 1
print(catalan(2))  # 2
print(catalan(3))  # 5
print(catalan(4))  # 14
print(catalan(5))  # 42