Dungeon Game

https://leetcode.com/problems/dungeon-game/

public class Solution {
    public int calculateMinimumHP(int[][] dungeon) {
       if (dungeon == null || dungeon.length == 0 || dungeon[0].length == 0) return 0;

    int m = dungeon.length;
    int n = dungeon[0].length;

    int[][] health = new int[m][n];

    health[m - 1][n - 1] = Math.max(1 - dungeon[m - 1][n - 1], 1);

    for (int i = m - 2; i >= 0; i--) {            
        health[i][n - 1] = Math.max(health[i + 1][n - 1] - dungeon[i][n - 1], 1);
    }

    for (int j = n - 2; j >= 0; j--) {
        health[m - 1][j] = Math.max(health[m - 1][j + 1] - dungeon[m - 1][j], 1);
    }

    for (int i = m - 2; i >= 0; i--) {
        for (int j = n - 2; j >= 0; j--) {
            int down = Math.max(health[i + 1][j] - dungeon[i][j], 1);
            int right = Math.max(health[i][j + 1] - dungeon[i][j], 1);
            health[i][j] = Math.min(right, down);
        }
    }

    return health[0][0]; 
    }
}