leetcode

0 class Solution {

1 public:

2 int numSubmatrixSumTarget(vector<vector<int>> &matrix, int target) const {

3 const int n = size(matrix), m = size(matrix[0]);

4

5 for (int i = 0; i < n; i++) {

6 for (int j = 0, acc = 0; j < m; j++) {

7 matrix[i][j] = acc += matrix[i][j];

8 }

9 }

10

11 unordered_map<int, int> um;

12 int res = 0;

13

14 for (int i = 0; i < m; i++) {

15 for (int j = i; j < m; j++) {

16 um = {{0, 1}};

17 int crnt = 0;

18 for (int k = 0; k < n; k++) {

19 crnt += matrix[k][j] - (i > 0 ? matrix[k][i - 1] : 0);

20 res += um[crnt - target];

21 um[crnt]++;

22 }

23 }

24 }

25

26 return res;

27 }

28 };