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Formatted question description: https://leetcode.ca/all/2536.html

2536. Increment Submatrices by One

Description

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, add 1 to mat[x][y] for all row1i <= x <= row2i and col1i <= 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

Solutions

  • class Solution {
    public int[][] rangeAddQueries(int n, int[][] queries) {
        int[][] mat = new int[n][n];
        for (var q : queries) {
            int x1 = q[0], y1 = q[1], x2 = q[2], y2 = q[3];
            mat[x1][y1]++;
            if (x2 + 1 < n) {
                mat[x2 + 1][y1]--;
            }
            if (y2 + 1 < n) {
                mat[x1][y2 + 1]--;
            }
            if (x2 + 1 < n && y2 + 1 < n) {
                mat[x2 + 1][y2 + 1]++;
            }
        }
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                if (i > 0) {
                    mat[i][j] += mat[i - 1][j];
                }
                if (j > 0) {
                    mat[i][j] += mat[i][j - 1];
                }
                if (i > 0 && j > 0) {
                    mat[i][j] -= mat[i - 1][j - 1];
                }
            }
        }
        return mat;
    }
}

  • class Solution {
public:
    vector<vector<int>> rangeAddQueries(int n, vector<vector<int>>& queries) {
        vector<vector<int>> mat(n, vector<int>(n));
        for (auto& q : queries) {
            int x1 = q[0], y1 = q[1], x2 = q[2], y2 = q[3];
            mat[x1][y1]++;
            if (x2 + 1 < n) {
                mat[x2 + 1][y1]--;
            }
            if (y2 + 1 < n) {
                mat[x1][y2 + 1]--;
            }
            if (x2 + 1 < n && y2 + 1 < n) {
                mat[x2 + 1][y2 + 1]++;
            }
        }
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                if (i > 0) {
                    mat[i][j] += mat[i - 1][j];
                }
                if (j > 0) {
                    mat[i][j] += mat[i][j - 1];
                }
                if (i > 0 && j > 0) {
                    mat[i][j] -= mat[i - 1][j - 1];
                }
            }
        }
        return mat;
    }
};

  • class Solution:
    def rangeAddQueries(self, n: int, queries: List[List[int]]) -> List[List[int]]:
        mat = [[0] * n for _ in range(n)]
        for x1, y1, x2, y2 in queries:
            mat[x1][y1] += 1
            if x2 + 1 < n:
                mat[x2 + 1][y1] -= 1
            if y2 + 1 < n:
                mat[x1][y2 + 1] -= 1
            if x2 + 1 < n and y2 + 1 < n:
                mat[x2 + 1][y2 + 1] += 1

        for i in range(n):
            for j in range(n):
                if i:
                    mat[i][j] += mat[i - 1][j]
                if j:
                    mat[i][j] += mat[i][j - 1]
                if i and j:
                    mat[i][j] -= mat[i - 1][j - 1]
        return mat


  • func rangeAddQueries(n int, queries [][]int) [][]int {
	mat := make([][]int, n)
	for i := range mat {
		mat[i] = make([]int, n)
	}
	for _, q := range queries {
		x1, y1, x2, y2 := q[0], q[1], q[2], q[3]
		mat[x1][y1]++
		if x2+1 < n {
			mat[x2+1][y1]--
		}
		if y2+1 < n {
			mat[x1][y2+1]--
		}
		if x2+1 < n && y2+1 < n {
			mat[x2+1][y2+1]++
		}
	}
	for i := 0; i < n; i++ {
		for j := 0; j < n; j++ {
			if i > 0 {
				mat[i][j] += mat[i-1][j]
			}
			if j > 0 {
				mat[i][j] += mat[i][j-1]
			}
			if i > 0 && j > 0 {
				mat[i][j] -= mat[i-1][j-1]
			}
		}
	}
	return mat
}

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