9/30 每日一題(計算矩陣兩個對角的總和)

 

Given a square matrix mat, return the sum of the matrix diagonals.

Only include the sum of all the elements on the primary diagonal and all the elements on the secondary diagonal that are not part of the primary diagonal.

 

Example 1:

Input: mat = [[1,2,3],
              [4,5,6],
              [7,8,9]]
Output: 25
Explanation: Diagonals sum: 1 + 5 + 9 + 3 + 7 = 25
Notice that element mat[1][1] = 5 is counted only once.

Example 2:

Input: mat = [[1,1,1,1],
              [1,1,1,1],
              [1,1,1,1],
              [1,1,1,1]]
Output: 8

Example 3:

Input: mat = [[5]]
Output: 5

 

Constraints:

• n == mat.length == mat[i].length
• 1 <= n <= 100
• 1 <= mat[i][j] <= 100

class Solution:

    def diagonalSum(self, mat: List[List[int]]) -> int:

        n=0

        N=len(mat)-1

        res=0

        for i in mat:

            a=i[n]

            b=i[N]

            print(f'a={a},b={b},n={n}, N={N}')

            if n==N:

                res+=a

               

            else:

                res+=a

                res+=b

            print(f'a={a},b={b}')

            print(f'目前總和={res}')

            print()

            n += 1

            N -= 1

        return res

----------------------------------------

class Solution:
    def diagonalSum(self, mat: List[List[int]]) -> int:
        result = 0
        for i in range(len(mat)):
            result += mat[i][i] + mat[i][len(mat) - i - 1]
            # print(mat[i][i], mat[i][len(mat) - i - 1], result)
        if len(mat) % 2 == 1:
            result -= mat[len(mat)//2][len(mat)//2]
        return result