LeetCode 1162: As Far from Land as Possible Solution

Master LeetCode problem 1162 (As Far from Land as Possible), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1162. As Far from Land as Possible

Medium

Array Dynamic Programming Breadth-First Search Matrix

Problem Explanation

Explanation:

Algorithmic Idea:
1. We start by iterating over the grid to find all land cells and add them to a queue.
2. Then we perform a BFS from each land cell to find the maximum distance to a water cell.
3. We keep track of the maximum distance found during the BFS.
4. Finally, we return the maximum distance as the result.
Time Complexity: O(n^2) where n is the size of the grid.
Space Complexity: O(n^2) for storing the queue and distances.

Solution Code

class Solution {
    public int maxDistance(int[][] grid) {
        int n = grid.length;
        Queue<int[]> queue = new LinkedList<>();
        
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == 1) {
                    queue.offer(new int[]{i, j});
                }
            }
        }
        
        int[][] directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
        int maxDistance = -1;
        
        while (!queue.isEmpty()) {
            int[] cell = queue.poll();
            for (int[] dir : directions) {
                int x = cell[0] + dir[0];
                int y = cell[1] + dir[1];
                if (x >= 0 && x < n && y >= 0 && y < n && grid[x][y] == 0) {
                    grid[x][y] = grid[cell[0]][cell[1]] + 1;
                    maxDistance = Math.max(maxDistance, grid[x][y] - 1);
                    queue.offer(new int[]{x, y});
                }
            }
        }
        
        return maxDistance;
    }
}

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