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Dp174.java
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48 lines (46 loc) · 1.58 KB
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package dynamicprogramming;
import java.util.Arrays;
/**
* @ProjectName: leetcode
* @Package: dynamicprogramming
* @ClassName: Dp174
* @Author: markey
* @Description:
* @Date: 2020/7/12 9:04
* @Version: 1.0
*/
public class Dp174 {
public int calculateMinimumHP(int[][] dungeon) {
if (dungeon.length == 0) {
return 1;
}
/**
* 从后往前进行状态转移
* 每个位置至少有1个点才不会死亡、
* 为了保证下个位置至少有x个点，则在上个位置时，至少有x-dungeon[i][j]个点，
* 这里想不明白可以按dungeon[i][j]是正负两个情况想一想，结果都是x-dungeon[i][j]
*/
int m = dungeon.length;
int n = dungeon[0].length;
int[][] min = new int[m][n];
// 初始化dp表
min[m - 1][n - 1] = Math.max(1 - dungeon[m - 1][n - 1], 1);
for (int i = m - 2; i >= 0; i--) {
min[i][n - 1] = Math.max(min[i + 1][n - 1] - dungeon[i][n - 1], 1); // 至少有1点
}
for (int i = n - 2; i >= 0; i--) {
min[m - 1][i] = Math.max(min[m - 1][i + 1] - dungeon[m - 1][i], 1); // 至少有1点
}
// 状态转移
for (int i = m - 2; i >= 0; i--) {
for (int j = n - 2; j >= 0; j--) {
int lastmin = Math.min(min[i + 1][j], min[i][j + 1]);
min[i][j] = Math.max(lastmin - dungeon[i][j], 1);
}
}
for (int i = 0; i < m; i++) {
System.out.println(Arrays.toString(min[i]));
}
return min[0][0];
}
}