"""
File: iteration.py
Created Time: 2023-08-24
Author: Krahets (krahets@163.com)
"""


def for_loop(n: int) -> int:
    """for 循环"""
    res = 0
    # 循环求和 1, 2, ..., n-1, n
    for i in range(1, n + 1):
        res += i
    return res


def while_loop(n: int) -> int:
    """while 循环"""
    res = 0
    i = 1  # 初始化条件变量
    # 循环求和 1, 2, ..., n-1, n
    while i <= n:
        res += i
        i += 1  # 更新条件变量
    return res


def while_loop_ii(n: int) -> int:
    """while 循环（两次更新）"""
    res = 0
    i = 1  # 初始化条件变量
    # 循环求和 1, 2, 4, 5...
    while i <= n:
        res += i
        i += 1  # 更新条件变量
        res += i
        i *= 2  # 更新条件变量
    return res


def nested_for_loop(n: int) -> str:
    """双层 for 循环"""
    res = ""
    # 循环 i = 1, 2, ..., n-1, n
    for i in range(1, n + 1):
        # 循环 j = 1, 2, ..., n-1, n
        for j in range(1, n + 1):
            res += f"({i}, {j}), "
    return res


"""Driver Code"""
if __name__ == "__main__":
    n = 5
    res = for_loop(n)
    print(f"\nfor 循环的求和结果 res = {res}")

    res = while_loop(n)
    print(f"\nwhile 循环的求和结果 res = {res}")

    res = while_loop_ii(n)
    print(f"\nwhile 循环（两次更新）求和结果 res = {res}")

    res = nested_for_loop(n)
    print(f"\n双层 for 循环的遍历结果 {res}")