1162. As Far from Land as Possible 

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class Solution {
    public int maxDistance(int[][] grid) {
        int n = grid.length;

        int MAX = 200;

        int[][] dp = new int[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == 0) {
                    dp[i][j] = MAX;
                }
            }
        }

        int maxDistance = 0;

        // 从左上角到右下角
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (i - 1 >= 0) {
                    dp[i][j] = Math.min(dp[i][j], dp[i - 1][j] + 1);
                }
                if (j - 1 >= 0) {
                    dp[i][j] = Math.min(dp[i][j], dp[i][j - 1] + 1);
                }
            }
        }

        // 从右下角到左上角
        for (int i = n - 1; i >= 0; i--) {
            for (int j = n - 1; j >= 0; j--) {
                if (i + 1 < n) {
                    dp[i][j] = Math.min(dp[i][j], dp[i + 1][j] + 1);
                }
                if (j + 1 < n) {
                    dp[i][j] = Math.min(dp[i][j], dp[i][j + 1] + 1);
                }

                if (grid[i][j] == 0) {
                    maxDistance = Math.max(maxDistance, dp[i][j]);
                }
            }
        }

        return maxDistance == 0 || maxDistance == MAX ? -1 : maxDistance;
    }
}

References

1162. As Far from Land as Possible