python经典案例:求矩阵主对方线之和

问题：求一个3x3矩阵主对角线元素之和。

实现方法：循环遍历矩阵，将主对角线上的元素相加

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
def main_diagonal_sum(matrix):
    if len(matrix) != 3 or any(len(row) != 3 for row in matrix):
        raise ValueError("输入的矩阵必须是3x3的")

    total = 0
    for i in range(3):
        for j in range(3):
            if i == j:
                total += matrix[i][j]

    return total

# 示例矩阵
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

result = main_diagonal_sum(matrix)
print("主对角线元素之和：", result)

优化方法：

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
def main_diagonal_sum(matrix):
    if len(matrix) != 3 or any(len(row) != 3 for row in matrix):
        raise ValueError("输入的矩阵必须是3x3的")

    sum = 0
    for i in range(3):#一次循环即可
        sum += matrix[i][i]
    return sum

# 示例矩阵
matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

result = main_diagonal_sum(matrix)
print("主对角线元素之和：", result)