blog/static/files/ib002/recursion/pyramid-slide-down/BottomUp.java
Matej Focko 84b080e343
ib002(recursion): add “Pyramid Slide Down”
Signed-off-by: Matej Focko <mfocko@redhat.com>
2023-08-17 00:14:48 +02:00

55 lines
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2 KiB
Java

import java.util.Arrays;
public class BottomUp {
public static int longestSlideDown(int[][] pyramid) {
int[][] slideDowns = new int[pyramid.length][];
slideDowns[pyramid.length - 1] = Arrays.copyOf(pyramid[pyramid.length - 1],
pyramid[pyramid.length - 1].length);
for (int y = pyramid.length - 2; y >= 0; --y) {
int[] row = Arrays.copyOf(pyramid[y], pyramid[y].length);
for (int x = 0; x < row.length; ++x) {
int under = slideDowns[y + 1][x];
int toRight = x + 1 < slideDowns[y + 1].length
? slideDowns[y + 1][x + 1]
: Integer.MIN_VALUE;
row[x] += Math.max(under, toRight);
}
slideDowns[y] = row;
}
return slideDowns[0][0];
}
public static void main(String[] args) {
System.out.print("Test #1: ");
System.out.println(longestSlideDown(new int[][] {
{ 3 },
{ 7, 4 },
{ 2, 4, 6 },
{ 8, 5, 9, 3 }
}) == 23 ? "passed" : "failed");
System.out.print("Test #2: ");
System.out.println(longestSlideDown(new int[][] {
{ 75 },
{ 95, 64 },
{ 17, 47, 82 },
{ 18, 35, 87, 10 },
{ 20, 4, 82, 47, 65 },
{ 19, 1, 23, 75, 3, 34 },
{ 88, 2, 77, 73, 7, 63, 67 },
{ 99, 65, 4, 28, 6, 16, 70, 92 },
{ 41, 41, 26, 56, 83, 40, 80, 70, 33 },
{ 41, 48, 72, 33, 47, 32, 37, 16, 94, 29 },
{ 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14 },
{ 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57 },
{ 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48 },
{ 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31 },
{ 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23 },
}) == 1074 ? "passed" : "failed");
}
}