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"title": "Matrix Block Sum",
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"content": "<p>Given a <code>m x n</code> matrix <code>mat</code> and an integer <code>k</code>, return <em>a matrix</em> <code>answer</code> <em>where each</em> <code>answer[i][j]</code> <em>is the sum of all elements</em> <code>mat[r][c]</code> <em>for</em>:</p>\n\n<ul>\n\t<li><code>i - k <= r <= i + k,</code></li>\n\t<li><code>j - k <= c <= j + k</code>, and</li>\n\t<li><code>(r, c)</code> is a valid position in the matrix.</li>\n</ul>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> mat = [[1,2,3],[4,5,6],[7,8,9]], k = 1\n<strong>Output:</strong> [[12,21,16],[27,45,33],[24,39,28]]\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> mat = [[1,2,3],[4,5,6],[7,8,9]], k = 2\n<strong>Output:</strong> [[45,45,45],[45,45,45],[45,45,45]]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>m == mat.length</code></li>\n\t<li><code>n == mat[i].length</code></li>\n\t<li><code>1 <= m, n, k <= 100</code></li>\n\t<li><code>1 <= mat[i][j] <= 100</code></li>\n</ul>\n",
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"code": "class Solution {\npublic:\n vector<vector<int>> matrixBlockSum(vector<vector<int>>& mat, int k) {\n \n }\n};",
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"code": "class Solution {\n public int[][] matrixBlockSum(int[][] mat, int k) {\n \n }\n}",
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"code": "class Solution(object):\n def matrixBlockSum(self, mat, k):\n \"\"\"\n :type mat: List[List[int]]\n :type k: int\n :rtype: List[List[int]]\n \"\"\"\n ",
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"code": "\n\n/**\n * Return an array of arrays of size *returnSize.\n * The sizes of the arrays are returned as *returnColumnSizes array.\n * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().\n */\nint** matrixBlockSum(int** mat, int matSize, int* matColSize, int k, int* returnSize, int** returnColumnSizes){\n\n}",
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"code": "/**\n * @param {number[][]} mat\n * @param {number} k\n * @return {number[][]}\n */\nvar matrixBlockSum = function(mat, k) {\n \n};",
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"lang": "Rust",
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"code": "impl Solution {\n pub fn matrix_block_sum(mat: Vec<Vec<i32>>, k: i32) -> Vec<Vec<i32>> {\n \n }\n}",
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"code": "(define/contract (matrix-block-sum mat k)\n (-> (listof (listof exact-integer?)) exact-integer? (listof (listof exact-integer?)))\n\n )",
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"hints": [
"How to calculate the required sum for a cell (i,j) fast ?",
"Use the concept of cumulative sum array.",
"Create a cumulative sum matrix where dp[i][j] is the sum of all cells in the rectangle from (0,0) to (i,j), use inclusion-exclusion idea."
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