Today I have done leetcode's May LeetCoding Challenge with cpp.

May LeetCoding Challenge 12

Description

Largest Local Values in a Matrix

You are given an n x n integer matrix grid.

Generate an integer matrix maxLocal of size (n - 2) x (n - 2) such that:

• maxLocal[i][j] is equal to the largest value of the 3 x 3 matrix in grid centered around row i + 1 and column j + 1.

In other words, we want to find the largest value in every contiguous 3 x 3 matrix in grid.

Return the generated matrix.

Example 1:

Input: grid = [[9,9,8,1],[5,6,2,6],[8,2,6,4],[6,2,2,2]]
Output: [[9,9],[8,6]]
Explanation: The diagram above shows the original matrix and the generated matrix.
Notice that each value in the generated matrix corresponds to the largest value of a contiguous 3 x 3 matrix in grid.

Example 2:

Input: grid = [[1,1,1,1,1],[1,1,1,1,1],[1,1,2,1,1],[1,1,1,1,1],[1,1,1,1,1]]
Output: [[2,2,2],[2,2,2],[2,2,2]]
Explanation: Notice that the 2 is contained within every contiguous 3 x 3 matrix in grid.

Constraints:

• n == grid.length == grid[i].length
• 3 <= n <= 100
• 1 <= grid[i][j] <= 100

Solution

class Solution {
public:
  vector<vector<int>> largestLocal(vector<vector<int>>& grid) {
    int rows = grid.size();
    int cols = grid.front().size();
    vector<vector<int>> answer;
    for(int i = 1; i < rows - 1; ++i) {
      answer.push_back({});
      for(int j = 1; j  < cols - 1; ++j) {
        int result = -100;
        for(int ii = i - 1; ii < i + 2; ++ii) {
          for(int jj = j - 1; jj < j + 2; ++jj) {
            result = max(result, grid[ii][jj]);
          }
        }
        answer.back().push_back(result);
      }
    }
    return answer;
  }
};