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ib002(recursion): add “Pyramid Slide Down”
Signed-off-by: Matej Focko <mfocko@redhat.com>
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6 changed files with 931 additions and 0 deletions
static/files/ib002/recursion/pyramid-slide-down
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static/files/ib002/recursion/pyramid-slide-down/.zipit
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static/files/ib002/recursion/pyramid-slide-down/.zipit
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import java.util.Arrays;
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public class BottomUp {
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public static int longestSlideDown(int[][] pyramid) {
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int[][] slideDowns = new int[pyramid.length][];
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slideDowns[pyramid.length - 1] = Arrays.copyOf(pyramid[pyramid.length - 1],
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pyramid[pyramid.length - 1].length);
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for (int y = pyramid.length - 2; y >= 0; --y) {
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int[] row = Arrays.copyOf(pyramid[y], pyramid[y].length);
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for (int x = 0; x < row.length; ++x) {
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int under = slideDowns[y + 1][x];
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int toRight = x + 1 < slideDowns[y + 1].length
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? slideDowns[y + 1][x + 1]
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: Integer.MIN_VALUE;
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row[x] += Math.max(under, toRight);
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}
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slideDowns[y] = row;
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}
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return slideDowns[0][0];
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}
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public static void main(String[] args) {
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System.out.print("Test #1: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 3 },
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{ 7, 4 },
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{ 2, 4, 6 },
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{ 8, 5, 9, 3 }
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}) == 23 ? "passed" : "failed");
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System.out.print("Test #2: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 75 },
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{ 95, 64 },
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{ 17, 47, 82 },
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{ 18, 35, 87, 10 },
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{ 20, 4, 82, 47, 65 },
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{ 19, 1, 23, 75, 3, 34 },
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{ 88, 2, 77, 73, 7, 63, 67 },
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{ 99, 65, 4, 28, 6, 16, 70, 92 },
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{ 41, 41, 26, 56, 83, 40, 80, 70, 33 },
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{ 41, 48, 72, 33, 47, 32, 37, 16, 94, 29 },
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{ 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14 },
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{ 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57 },
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{ 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48 },
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{ 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31 },
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{ 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23 },
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}) == 1074 ? "passed" : "failed");
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}
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}
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47
static/files/ib002/recursion/pyramid-slide-down/Greedy.java
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static/files/ib002/recursion/pyramid-slide-down/Greedy.java
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public class Greedy {
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public static int longestSlideDown(int[][] pyramid, int row, int col) {
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if (row == pyramid.length - 1) {
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return pyramid[row][col];
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}
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if (col + 1 >= pyramid[row + 1].length
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|| pyramid[row + 1][col] > pyramid[row + 1][col + 1]) {
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return pyramid[row][col] + longestSlideDown(pyramid, row + 1, col);
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}
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return pyramid[row][col] + longestSlideDown(pyramid, row + 1, col + 1);
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}
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public static int longestSlideDown(int[][] pyramid) {
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return longestSlideDown(pyramid, 0, 0);
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}
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public static void main(String[] args) {
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System.out.print("Test #1: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 3 },
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{ 7, 4 },
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{ 2, 4, 6 },
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{ 8, 5, 9, 3 }
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}) == 23 ? "passed" : "failed");
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System.out.print("Test #2: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 75 },
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{ 95, 64 },
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{ 17, 47, 82 },
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{ 18, 35, 87, 10 },
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{ 20, 4, 82, 47, 65 },
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{ 19, 1, 23, 75, 3, 34 },
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{ 88, 2, 77, 73, 7, 63, 67 },
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{ 99, 65, 4, 28, 6, 16, 70, 92 },
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{ 41, 41, 26, 56, 83, 40, 80, 70, 33 },
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{ 41, 48, 72, 33, 47, 32, 37, 16, 94, 29 },
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{ 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14 },
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{ 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57 },
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{ 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48 },
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{ 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31 },
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{ 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23 },
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}) == 1074 ? "passed" : "failed");
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}
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}
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48
static/files/ib002/recursion/pyramid-slide-down/Naive.java
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static/files/ib002/recursion/pyramid-slide-down/Naive.java
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public class Naive {
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public static int longestSlideDown(int[][] pyramid, int row, int col) {
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if (row >= pyramid.length || col < 0 || col >= pyramid[row].length) {
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return Integer.MIN_VALUE;
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}
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if (row == pyramid.length - 1) {
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return pyramid[row][col];
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}
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return pyramid[row][col] + Math.max(
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longestSlideDown(pyramid, row + 1, col),
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longestSlideDown(pyramid, row + 1, col + 1));
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}
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public static int longestSlideDown(int[][] pyramid) {
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return longestSlideDown(pyramid, 0, 0);
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}
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public static void main(String[] args) {
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System.out.print("Test #1: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 3 },
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{ 7, 4 },
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{ 2, 4, 6 },
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{ 8, 5, 9, 3 }
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}) == 23 ? "passed" : "failed");
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System.out.print("Test #2: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 75 },
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{ 95, 64 },
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{ 17, 47, 82 },
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{ 18, 35, 87, 10 },
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{ 20, 4, 82, 47, 65 },
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{ 19, 1, 23, 75, 3, 34 },
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{ 88, 2, 77, 73, 7, 63, 67 },
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{ 99, 65, 4, 28, 6, 16, 70, 92 },
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{ 41, 41, 26, 56, 83, 40, 80, 70, 33 },
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{ 41, 48, 72, 33, 47, 32, 37, 16, 94, 29 },
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{ 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14 },
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{ 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57 },
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{ 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48 },
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{ 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31 },
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{ 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23 },
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}) == 1074 ? "passed" : "failed");
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}
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}
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76
static/files/ib002/recursion/pyramid-slide-down/TopDown.java
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76
static/files/ib002/recursion/pyramid-slide-down/TopDown.java
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import java.util.TreeMap;
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public class TopDown {
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record Position(int row, int col) implements Comparable<Position> {
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public int compareTo(Position r) {
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if (row != r.row) {
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return Integer.valueOf(row).compareTo(r.row);
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}
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if (col != r.col) {
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return Integer.valueOf(col).compareTo(r.col);
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}
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return 0;
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}
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}
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public static int longestSlideDown(
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int[][] pyramid,
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TreeMap<Position, Integer> cache,
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Position position) {
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int row = position.row;
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int col = position.col;
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if (row >= pyramid.length || col < 0 || col >= pyramid[row].length) {
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return Integer.MIN_VALUE;
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}
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if (row == pyramid.length - 1) {
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return pyramid[position.row][position.col];
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}
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if (!cache.containsKey(position)) {
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int slideDown = Math.max(
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longestSlideDown(pyramid, cache, new Position(row + 1, col)),
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longestSlideDown(pyramid, cache, new Position(row + 1, col + 1)));
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cache.put(position, pyramid[row][col] + slideDown);
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}
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return cache.get(position);
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}
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public static int longestSlideDown(int[][] pyramid) {
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TreeMap<Position, Integer> cache = new TreeMap<>();
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return longestSlideDown(pyramid, cache, new Position(0, 0));
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}
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public static void main(String[] args) {
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System.out.print("Test #1: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 3 },
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{ 7, 4 },
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{ 2, 4, 6 },
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{ 8, 5, 9, 3 }
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}) == 23 ? "passed" : "failed");
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System.out.print("Test #2: ");
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System.out.println(longestSlideDown(new int[][] {
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{ 75 },
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{ 95, 64 },
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{ 17, 47, 82 },
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{ 18, 35, 87, 10 },
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{ 20, 4, 82, 47, 65 },
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{ 19, 1, 23, 75, 3, 34 },
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{ 88, 2, 77, 73, 7, 63, 67 },
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{ 99, 65, 4, 28, 6, 16, 70, 92 },
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{ 41, 41, 26, 56, 83, 40, 80, 70, 33 },
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{ 41, 48, 72, 33, 47, 32, 37, 16, 94, 29 },
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{ 53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14 },
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{ 70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57 },
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{ 91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48 },
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{ 63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31 },
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{ 4, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23 },
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}) == 1074 ? "passed" : "failed");
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}
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}
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