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

October LeetCoding Challenge 29

Description

Rotting Oranges

You are given an m x n grid where each cell can have one of three values:

• 0 representing an empty cell,
• 1 representing a fresh orange, or
• 2 representing a rotten orange.

Every minute, any fresh orange that is 4-directionally adjacent to a rotten orange becomes rotten.

Return the minimum number of minutes that must elapse until no cell has a fresh orange. If this is impossible, return -1.

Example 1:

Input: grid = [[2,1,1],[1,1,0],[0,1,1]]
Output: 4

Example 2:

Input: grid = [[2,1,1],[0,1,1],[1,0,1]]
Output: -1
Explanation: The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally.

Example 3:

Input: grid = [[0,2]]
Output: 0
Explanation: Since there are already no fresh oranges at minute 0, the answer is just 0.

Constraints:

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 10
• grid[i][j] is 0, 1, or 2.

Solution

const int moves[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
class Solution {
public:
  int orangesRotting(vector<vector<int>>& grid) {
    queue<pair<int, int>> q;
    int rows = grid.size();
    int cols = grid.front().size();
    for(int i = 0; i < rows; ++i) {
      for(int j = 0; j < cols; ++j) {
        if(grid[i][j] == 2) q.push({i, j});
      }
    }

    while(q.size()) {
      auto [row, col] = q.front();
      q.pop();
      for(int m = 0; m < 4; ++m) {
        int newRow = row + moves[m][0];
        int newCol = col + moves[m][1];
        if(newRow < 0 || newRow >= rows || newCol >= cols || newCol < 0) continue;
        if(grid[newRow][newCol] != 1) continue;
        grid[newRow][newCol] = grid[row][col] + 1;
        q.push({newRow, newCol});
      }
    }

    int answer = 2;
    for(int i = 0; i < rows; ++i) {
      for(int j = 0; j < cols; ++j) {
        if(grid[i][j] == 1) return -1;
        answer = max(answer, grid[i][j]);
      }
    }

    return answer - 2;
  }
};

// Accepted
// 306/306 cases passed (4 ms)
// Your runtime beats 92.11 % of cpp submissions
// Your memory usage beats 50.83 % of cpp submissions (13.1 MB)