LeetCode – Dungeon Game (Java)

Example:

-2 (K)	-3	3
-5	-10	1
10	30	-5 (P)

Java Solution

This problem can be solved by using dynamic programming. We maintain a 2-D table. h[i][j] is the minimum health value before he enters (i,j). h[0][0] is the value of the answer. The left part is filling in numbers to the table.

public int calculateMinimumHP(int[][] dungeon) {
	int m = dungeon.length;
	int n = dungeon[0].length;
 
	//init dp table
	int[][] h = new int[m][n];
 
	h[m - 1][n - 1] = Math.max(1 - dungeon[m - 1][n - 1], 1);
 
	//init last row
	for (int i = m - 2; i >= 0; i--) {
		h[i][n - 1] = Math.max(h[i + 1][n - 1] - dungeon[i][n - 1], 1);
	}
 
	//init last column
	for (int j = n - 2; j >= 0; j--) {
		h[m - 1][j] = Math.max(h[m - 1][j + 1] - dungeon[m - 1][j], 1);
	}
 
	//calculate dp table
	for (int i = m - 2; i >= 0; i--) {
		for (int j = n - 2; j >= 0; j--) {
			int down = Math.max(h[i + 1][j] - dungeon[i][j], 1);
			int right = Math.max(h[i][j + 1] - dungeon[i][j], 1);
			h[i][j] = Math.min(right, down);
		}
	}
 
	return h[0][0];
}
Category >> Algorithms >> Interview  
If you want someone to read your code, please put the code inside <pre><code> and </code></pre> tags. For example:
<pre><code> 
String foo = "bar";
</code></pre>

  1. Arnaud Hebert on 2015-5-14

    Is it possible to have more information about the game itself? (the purpose of the game, the meaning of the numbers, meaning of K, meaning of P). I was not able to look it up online

  2. stellari on 2015-5-24

    The purpose of the game is for a Knight(K) to traverse a dungeon full of threats and power-ups to rescue the princess(P). You can find the full problem description on oj.leetcode.com in the problem “Dungeon Game”. It is not surprising you can’t find the problem because I (yes, I am the creator of this problem on leetcode) wrote the original problem description in my own language, and apparently it hasn’t gain enough popularity on the web yet.

  3. typing.. on 2015-8-2

    Attempt this problem if you want to brush up your DP concepts.. Very Nice problem.. and even perfect solution.. Thumbs Up 🙂

  4. Candis on 2015-10-29

    Loved the answer! 🙂

  5. omnomnipotent on 2016-7-23

    Thank you Stellari – you would think that this information would be presented up front. To Programcreek – don’t assume that everyone knows what this type of problem is; a simple explanation would do and save trouble for everyone.

  6. Ing on 2016-10-17

    Got here from google and I can see an answer, but not the problem it answers…

Leave a comment

*