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Matrix Block Sum
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Brute Force
2D Prefix Sum
Input
3x3, k=1
3x3, k=2
3x4, k=1
2x2, k=1
Custom
mat
=
[[1,2,3],[4,5,6],[7,8,9]]
,
k
=
1
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
answer[0][0] = sum of mat[0..1][0..1] =
12
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
answer[0][1] = sum of mat[0..1][0..2] =
21
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
answer[0][2] = sum of mat[0..1][1..2] =
16
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
answer[1][0] = sum of mat[0..2][0..1] =
27
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
45
33
answer[1][2] = sum of mat[0..2][1..2] =
33
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
45
33
24
answer[2][0] = sum of mat[1..2][0..1] =
24
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
45
33
24
39
answer[2][1] = sum of mat[1..2][0..2] =
39
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
45
33
24
39
28
answer[2][2] = sum of mat[1..2][1..2] =
28
k =
1
mat
answer
0
0
1
1
2
2
0
1
2
1
2
3
4
5
6
7
8
9
12
21
16
27
45
33
24
39
28
All block sums computed
algo
master
.
io
Step:
Start: for each cell, add up its clamped k = 1 block one cell at a time
0 / 10
Input
3x3, k=1
3x3, k=2
3x4, k=1
2x2, k=1
Custom
mat
=
[[1,2,3],[4,5,6],[7,8,9]]
,
k
=
1
0 / 10
algo
master
.
io
Step:
Start: for each cell, add up its clamped k = 1 block one cell at a time
