1314. Matrix Block Sum

https://leetcode.com/problems/matrix-block-sum

Description

Given a m x n matrix mat and an integer k, return a matrix answer where each answer[i][j] is the sum of all elements mat[r][c] for:

• i - k <= r <= i + k,

• j - k <= c <= j + k, and

• (r, c) is a valid position in the matrix.

Example 1:

**Input:** mat = [[1,2,3],[4,5,6],[7,8,9]], k = 1
**Output:** [[12,21,16],[27,45,33],[24,39,28]]

Example 2:

**Input:** mat = [[1,2,3],[4,5,6],[7,8,9]], k = 2
**Output:** [[45,45,45],[45,45,45],[45,45,45]]

Constraints:

• m == mat.length

• n == mat[i].length

• 1 <= m, n, k <= 100

• 1 <= mat[i][j] <= 100

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