Submatrices with target sum
Given an m x n integer matrix and an integer `target`, return the number of non-empty submatrices (contiguous rectangular blocks) whose elements sum to exactly `target`. Values may be negative. m, n are up to 100. A brute force over all O(m^2 n^2) rectangles is too slow; collapse one dimension with prefix sums and use the subarray-sum-equals-k hashing trick on the other.
Implement
num_submatrix_sum_target(matrix: list[list[int]], target: int) → intExamples
in
[[[0,1,0],[1,1,1],[0,1,0]],0]out4What a strong answer looks like
State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
0:00 of about 35 min
solution.py
InputExpectedGot
[[[0,1,0],[1,1,1],[0,1,0]],0]4not run yetsample