- Difficulty: Medium
- Tags: LeetCode, Medium, Array, Matrix, Prefix Sum, leetcode-2536, O(q + n^2), O(1), Line Sweep, Difference Matrix, Difference Array
Problem
You are given a positive integer n
, indicating that we initially have an n x n
0-indexed integer matrix mat
filled with zeroes.
You are also given a 2D integer array query
. For each query[i] = [row1i, col1i, row2i, col2i]
, you should do the following operation:
- Add
1
to every element in the submatrix with the top left corner(row1i, col1i)
and the bottom right corner(row2i, col2i)
. That is, add1
tomat[x][y]
for allrow1i <= x <= row2i
andcol1i <= y <= col2i
.
Return the matrix mat
after performing every query.
Example 1:
Input: n = 3, queries = [[1,1,2,2],[0,0,1,1]] Output: [[1,1,0],[1,2,1],[0,1,1]] Explanation: The diagram above shows the initial matrix, the matrix after the first query, and the matrix after the second query. - In the first query, we add 1 to every element in the submatrix with the top left corner (1, 1) and bottom right corner (2, 2). - In the second query, we add 1 to every element in the submatrix with the top left corner (0, 0) and bottom right corner (1, 1).
Example 2:
Input: n = 2, queries = [[0,0,1,1]] Output: [[1,1],[1,1]] Explanation: The diagram above shows the initial matrix and the matrix after the first query. - In the first query we add 1 to every element in the matrix.
Constraints:
1 <= n <= 500
1 <= queries.length <= 104
0 <= row1i <= row2i < n
0 <= col1i <= col2i < n