DP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
| class Solution {
public int minFallingPathSum(int[][] grid) {
int n = grid.length;
for (int i = 1; i < n; i++) {
for (int j = 0; j < n; j++) {
int min = Integer.MAX_VALUE;
for (int k = 0; k < n; k++) {
if (k == j) {
continue;
}
min = Math.min(min, grid[i - 1][k]);
}
grid[i][j] += min;
}
}
int minPathSum = Integer.MAX_VALUE;
for (int j = 0; j < n; j++) {
minPathSum = Math.min(minPathSum, grid[n - 1][j]);
}
return minPathSum;
}
}
|
DP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
| class Solution {
public int minFallingPathSum(int[][] grid) {
int n = grid.length;
int firstMinIndex = -1, secondMinIndex = -1;
for (int j = 0; j < n; j++) {
int num = grid[0][j];
if (num < (firstMinIndex == -1 ? Integer.MAX_VALUE : grid[0][firstMinIndex])) {
secondMinIndex = firstMinIndex;
firstMinIndex = j;
} else if (num < (secondMinIndex == -1 ? Integer.MAX_VALUE : grid[0][secondMinIndex])) {
secondMinIndex = j;
}
}
for (int i = 1; i < n; i++) {
int tempFirstMinIndex = -1, tempSecondMinIndex = -1;
for (int j = 0; j < n; j++) {
if (j == firstMinIndex) {
grid[i][j] += grid[i - 1][secondMinIndex];
} else {
grid[i][j] += grid[i - 1][firstMinIndex];
}
int num = grid[i][j];
if (num < (tempFirstMinIndex == -1 ? Integer.MAX_VALUE : grid[i][tempFirstMinIndex])) {
tempSecondMinIndex = tempFirstMinIndex;
tempFirstMinIndex = j;
} else if (num < (tempSecondMinIndex == -1 ? Integer.MAX_VALUE : grid[i][tempSecondMinIndex])) {
tempSecondMinIndex = j;
}
}
firstMinIndex = tempFirstMinIndex;
secondMinIndex = tempSecondMinIndex;
}
int minPathSum = Integer.MAX_VALUE;
for (int j = 0; j < n; j++) {
minPathSum = Math.min(minPathSum, grid[n - 1][j]);
}
return minPathSum;
}
}
|
References
1289. Minimum Falling Path Sum II