Leetcode7.12地下城游戏 动态规划

**class Solution {
public:
    int calculateMinimumHP(vector<vector<int>>& dungeon) {
        int M = dungeon.size();
        int N = dungeon[0].size();
        int dp[M][N];
        dp[M-1][N-1] = dungeon[M-1][N-1]  > 0 ? 1: -dungeon[M-1][N-1] + 1;
        for(int i = M - 1; i >=0 ;i--){
            for(int j = N -1; j >=0; j--){
                if(i == M -1 && j != N-1){
                    dp[i][j] = dungeon[i][j] - dp[i][j + 1]  >= 0 ? 1 : dp[i][j+1] - dungeon[i][j];
                }
                else if(j == N-1 && i != M - 1){
                    dp[i][j] = dungeon[i][j] - dp[i + 1][j]  >= 0 ? 1 : dp[i + 1][j] - dungeon[i][j];
                }
                else if(j!=N-1 && i!=M-1){
                    dp[i][j] = min(dungeon[i][j] - dp[i][j + 1]  >= 0 ? 1 : dp[i][j+1] - dungeon[i][j] , dungeon[i][j] - dp[i + 1][j]  >= 0 ? 1 : dp[i + 1][j] - dungeon[i][j]);
                }
                
            }
        }
        return dp[0][0];
    }
};**

官方题解，是真的简洁！

class Solution {
public:
    int calculateMinimumHP(vector<vector<int>>& dungeon) {
        int n = dungeon.size(), m = dungeon[0].size();
        vector<vector<int>> dp(n + 1, vector<int>(m + 1, INT_MAX));
        dp[n][m - 1] = dp[n - 1][m] = 1;
        for (int i = n - 1; i >= 0; --i) {
            for (int j = m - 1; j >= 0; --j) {
                int minn = min(dp[i + 1][j], dp[i][j + 1]);
                dp[i][j] = max(minn - dungeon[i][j], 1);
            }
        }
        return dp[0][0];
    }
};