int calculateMinimumHP(vector<vector<int> > &dungeon) {
int n = dungeon.size();
if(n==0) return 0;
int m = dungeon[0].size();
if(m==0) return 0;
vector<int> minHP(m);
for(int i=m-1;i>=0;i--) {
if(i==m-1) minHP[i] = dungeon[n-1][m-1]>=0 ? 1: - dungeon[n-1][m-1]+1;
else {
int needed = minHP[i+1] - dungeon[n-1][i];
minHP[i] = needed > 0 ? needed : 1;
}
}
for(int i=n-2;i>=0;i--) {
for(int j=m-1;j>=0;j--) {
if(j==m-1) {
int needed = minHP[m-1] - dungeon[i][j];
minHP[m-1] = needed > 0 ? needed : 1;
} else {
int right = minHP[j+1] - dungeon[i][j];
int bottom = minHP[j] - dungeon[i][j];
minHP[j] = max(min(right, bottom), 1);
}
}
}
return minHP[0];
}
int calculateMinimumHP(vector<vector<int> > &dungeon) {
size_t m = dungeon.size();
size_t n = dungeon[0].size();
int d[m][n] = { 0 };
d[m - 1][n - 1] = minHP(1 - dungeon[m - 1][n - 1]);
for (int i = m - 2; i >= 0; --i) {
d[i][n - 1] = minHP(d[i + 1][n - 1] - dungeon[i][n - 1]);
}
for (int j = n - 2; j >= 0; --j) {
d[m - 1][j] = minHP(d[m - 1][j + 1] - dungeon[m - 1][j]);
}
for (int i = m - 2; i >= 0; --i) {
for (int j = n - 2; j >= 0; --j) {
d[i][j] = minHP(min(d[i + 1][j], d[i][j + 1]) - dungeon[i][j]);
}
}
return d[0][0];
}
