Dungeon Game.cpp added

C++/dungeon-game.cpp

@@ -0,0 +1,64 @@
+//https://leetcode.com/problems/dungeon-game/
+////Difficulty Level: Hard
+//Tags: Dynamic Programming
+//Time complexity: O(m*n)
+//Space complexity: O(m*n)
+//bottom-up DP approach
+class Solution 
+{
+    public:
+    int calculateMinimumHP(vector<vector<int>>& dungeon) 
+    {
+        int m = dungeon.size();
+        if(r==0)                //empty dungeon
+           return 0;
+
+        int n = dungeon[0].size();
+
+        //dp[i][j] --> min health req to reach the princess with starting cell as (i,j) -1
+        vector<vector<int> > dp(r, vector<int>(c));
+
+        for (int i = m-1; i>=0; i--)          //traversing the array from bottom
+        {
+            for (int j = n-1; j>=0; j--)
+            {
+                //if starting from last cell, 
+                //if value at last cell is -ve, health req. is 1+abs(value)
+                //if value at last cell is +ve, health req. is 0+1
+                if (i == m-1 && j == n-1)     
+                {
+                    dp[i][j] = min(0, dungeon[i][j]);
+                }
+
+                //if starting from last row,
+                //total health req. is sum of curr cell value and health req. at next cell
+                //if the sum is +ve, health req. is 0+1
+                //if the sum is -ve, health req. is 1+abs(sum)
+                else if (i == m-1)
+                {
+                    dp[i][j] = min(0, dungeon[i][j]+dp[i][j+1]);
+                }
+
+                //if starting from last column,
+                //total health req. is sum of curr cell value and health req. at next cell
+                //if the sum is +ve, health req. is 0+1
+                //if the sum is -ve, health req. is 1+abs(sum)
+                else if (j == n-1)
+                {
+                    dp[i][j] = min(0, dungeon[i][j]+dp[i+1][j]);
+                }
+
+                //if starting from any other cell,
+                //make a choice to go to the cell with less req. health(more positive dp value) after the curr cell
+                //the req. health is either 0 or sum of the curr cell value and health req. at next chosen cell
+                else
+                {
+                    dp[i][j] = min(0, dungeon[i][j]+max(dp[i][j+1],dp[i+1][j]));
+                }
+            }
+        }
+        //actual starting point is (0,0), so return abs(dp(0,0))+1
+        //1 is added because the knight needs to have atleast 1 health to survive, else he will die
+        return abs(dp[0][0])+1;
+    }
+};

README.md

@@ -203,8 +203,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | 242 | [Valid Anagram](https://leetcode.com/problems/valid-anagram/) | [Java](./Java/valid-anagram.java)                               | _O(n)_ | _O(1)_ | Easy       |     | [Tutorial](https://www.youtube.com/watch?v=sbX1Ze9lNQE) |
 | 146 | [LRU Cache](https://leetcode.com/problems/lru-cache/)         | [Java](./Java/LRU-Cache.java)                                   |        |        | Medium     |     |                                                         |
 | 217 | [Contains Duplicate](https://leetcode.com/problems/contains-duplicate/)         | [Python](./Python/contains-duplicate.py)      | _O(n)_ | _O(n)_ |            |     |
-| 554 | [Brick Wall](https://leetcode.com/problems/brick-wall/) |
-[C++](./C++/brick-walls.cpp)| _O(n)_ | _O(n)_ | Medium     |     |
+| 554 | [Brick Wall](https://leetcode.com/problems/brick-wall/) | [C++](./C++/brick-walls.cpp)| _O(n)_ | _O(n)_ | Medium     |     |
 
 <br/>
 <div align="right">
@@ -292,8 +291,10 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | 72   | [Edit Distance](https://leetcode.com/problems/edit-distance/)                                 | [Python](./Python/edit-distance.py)            | _O(N\*M)_ | _O(n^2)_ | Medium     | Levenshtein Distance |      |
 | 91   | [Decode ways](https://leetcode.com/problems/decode-ways/)                                     | [Python](./Python/decode-ways.py)              | _O(N)_    | _O(N)_   | Easy       | DP                   |      |
 | 1025 | [Divisor Game](https://leetcode.com/problems/divisor-game/)                                   | [Python](./Python/divisor-game.py)             | _O(N^2)_  | _O(N)_   | Easy       | DP                   |      |
+| 174 | [Dungeon Game](https://leetcode.com/problems/dungeon-game/)                                   | [C++](./C++/dungeon-game.pp)             | _O(M*N)_  | _O(M*N)_   | Hard       | Dynamic Programming                  |    |
 | 070 | [Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)                                   | [Java](./Java/climbing-stairs.java)             | _O(N)_  | _O(1)_  | Easy       | DP                   |      |
 
+
 <br/>
 <div align="right">
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