- Difficulty: Medium
- Tags: LeetCode, Medium, Array, Matrix, Prefix Sum, leetcode-1314, Dynamic Programming, O(m * n)
Problem
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