java 174. Dungeon Game（＃1）.java

Posted 2021-05-08

public class Solution {
    private int result = Integer.MAX_VALUE;
    private int[][] dirs = {{1,0}, {0,1}};
    public int calculateMinimumHP(int[][] dungeon) {
        int[][] cache = new int[dungeon.length][dungeon[0].length];
        int res = dfs(dungeon, 0, 0, cache);
        return res > 0 ? 1 : ((-1)*res+1);
        
    }

    private int dfs(int[][] dungeon, int x, int y, int[][] cache) {
        if(x == dungeon.length-1 && y == dungeon[0].length-1) {
            return dungeon[x][y] > 0 ? 0 : dungeon[x][y];
        }

        if(cache[x][y] != 0) {
            return cache[x][y] == -1 ? 0 : cache[x][y];
        }
        
        int result = Integer.MIN_VALUE;
        for(int[] dir : dirs) {
            int x0 = x + dir[0];
            int y0 = y + dir[1];

            if(x0 >= dungeon.length || y0 >= dungeon[0].length) {
                continue;
            }
            result = Math.max(result, dfs(dungeon, x0, y0, cache));
        }
        
        cache[x][y] = (result+dungeon[x][y]) > 0 ? -1 : (result+dungeon[x][y]);
        return (result+dungeon[x][y]) > 0 ? 0 : (result+dungeon[x][y]);
    }
}

public class Solution {
    public int calculateMinimumHP(int[][] dungeon) {
        int res = Integer.MAX_VALUE;
        if (dungeon == null || dungeon.length < 1 || dungeon[0].length < 1) return res;
        int row = dungeon.length;
        int col = dungeon[0].length;
        int[][] dp = new int[row + 1][col + 1];
        for (int i = 0; i <= row; i++) {
             Arrays.fill(dp[i], Integer.MAX_VALUE);
        }
        
        dp[row][col - 1] = 1;
        dp[row - 1][col] = 1;
        //dp[row - 1][col - 1] = 0;
        for (int i = row - 1; i >= 0; i--) {
            for (int j = col - 1; j >= 0; j--) {
                if (dungeon[i][j] >= dp[i + 1][j] || dungeon[i][j] >= dp[i][j + 1]) {
                    dp[i][j] = 1;
                } else {
                    dp[i][j] = Math.min(dp[i + 1][j], dp[i][j + 1]) - dungeon[i][j];
                }
            }
        }
        return dp[0][0];
    }
}