Leetcode Dungeon Game

The original title link is here: https://leetcode.com/problems/dungeon-game/

This is a DP problem, save the current grid to the bottom right of the minimum required strength, M*n DP array saved.

The update is math.min (take the right hand minimum strength, the lower left side of the minimum strength). Take the right hand minimum strength = Math.max (dp[i][j+1]-dungeon[i][j], 0). Suppose always dp[i][j+1] = 3, dungeon[i][j] =-5, 3-(-5) = 8 is the minimum required to go to the right, but if dp[i][j+1] = 3, dungeon[i][j] = 8, 3-8 = 5, the currently eaten magic Bean adds 8 points Physical strength, you do not need the minimum physical value can go to the right, so the minimum energy required is 0. Go down similarly.

First show the bottom right point, then the last row and the last column.

Note:1. The last return is not dp[0][0], but dp[0][0] plus one, because the minimum value of the previously obtained physical value is 0, but the knight's physical strength must be a positive number.

2. The reason for choosing to update from back to front rather than from the back is because the local optimal is not guaranteed to be the global optimal when the former is updated.

AC Java:

1  Public classSolution {2      Public intCALCULATEMINIMUMHP (int[] Dungeon) {3         if(Dungeon = =NULL|| Dungeon.length = = 0 | | Dungeon[0].length = = 0){4             return0;5         }6         intm =dungeon.length;7         intn = dungeon[0].length;8         int[] DP =New int[m][n];9Dp[m-1][n-1] = Dungeon[m-1][n-1] < 0? -dungeon[m-1][n-1]:0;Ten          for(inti = m-2; i>=0; i--){ OneDp[i][n-1] = dp[i+1][n-1]-dungeon[i][n-1] > 0? DP[I+1][N-1]-dungeon[i][n-1]: 0; A         } -          for(intj = n-2; j>=0; j--){ -DP[M-1][J] = dp[m-1][j+1]-dungeon[m-1][j] > 0? DP[M-1][J+1]-Dungeon[m-1][j]: 0; the         } -          for(inti = m-2; i>=0; i--){ -              for(intj = n-2; j>=0; j--){ -DP[I][J] = Math.min ((dp[i+1][j]-dungeon[i][j] > 0? DP[I+1][J]-dungeon[i][j]: 0), (dp[i][j+1]-dungeon[i][j] > 0? dp[i][j+1]-dungeon[i][j]: 0)); +             } -         } +         returnDp[0][0]+1; A     } at}

Leetcode Dungeon Game