题目：原题链接（中等）

解法	时间复杂度	空间复杂度	执行用时
Ans 1 (Python)	O ( M × N ) O(M×N) O(M×N)	O ( M × N ) O(M×N) O(M×N)	1224ms (71.14%)
Ans 2 (Python)
Ans 3 (Python)

解法一：

class Solution:
    def matrixBlockSum(self, mat: List[List[int]], K: int) -> List[List[int]]:
        m, n = len(mat), len(mat[0])

        # 计算前缀和
        prefix = [[0] * (n + 1) for _ in range(m + 1)]
        for i in range(1, m + 1):
            for j in range(1, n + 1):
                prefix[i][j] = prefix[i - 1][j] + prefix[i][j - 1] - prefix[i - 1][j - 1] + mat[i - 1][j - 1]

        # 计算范围内的和
        def count(x1, y1, x2, y2):
            return prefix[x2][y2] - prefix[x1 - 1][y2] - prefix[x2][y1 - 1] + prefix[x1 - 1][y1 - 1]

        ans = [[0] * n for _ in range(m)]
        for i in range(m):
            for j in range(n):
                ans[i][j] += count(max(i - K, 0) + 1, max(j - K, 0) + 1, min(i + K, m - 1) + 1, min(j + K, n - 1) + 1)
        return ans