Leetcode Problem 1314. Matrix Block Sum

1314. Matrix Block Sum

Leetcode Solutions

Prefix Sum Approach

  1. Initialize a matrix prefixSum with the same dimensions as mat, plus one extra row and column filled with zeros.
  2. Populate prefixSum by calculating the cumulative sum for each cell based on the values to the left, above, and diagonally above-left.
  3. Initialize the result matrix answer with the same dimensions as mat.
  4. Iterate over each cell (i,j) in mat.
  5. For each cell, determine the boundaries of the k-distance neighborhood, clamped within the matrix dimensions.
  6. Calculate the sum for the neighborhood using the prefix sums of the relevant corners.
  7. Assign the calculated sum to the corresponding cell in answer.
  8. Return the answer matrix.
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Brute Force Approach

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