From 880f1b2d2c4cb32f9ced98d447e131de57c7e9fb Mon Sep 17 00:00:00 2001
From: Trishun <piotr_dec@msn.com>
Date: Sat, 5 Nov 2022 21:59:49 +0100
Subject: [PATCH] Resolves Java 1D Array Pt.2 Task

---
 .../datastructures/array_1d_pt2/Solution.java | 63 ++++++++++++++
 .../array_1d_pt2/SolutionTest.java            | 83 +++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 src/main/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/Solution.java
 create mode 100644 src/test/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/SolutionTest.java

diff --git a/src/main/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/Solution.java b/src/main/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/Solution.java
new file mode 100644
index 0000000..7cc86ab
--- /dev/null
+++ b/src/main/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/Solution.java
@@ -0,0 +1,63 @@
+package eu.ztsh.training.hackerrank.datastructures.array_1d_pt2;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class Solution {
+
+    public static boolean canWin(int leap, int[] game) {
+        return move(0, leap, game, new int[]{});
+    }
+
+    static boolean isWinningMove(int index, int leap, int length) {
+        return index == length - 1 || index + leap > length - 1;
+    }
+
+    static boolean canMoveForward(int index, int[] game) {
+        return game[index + 1] == 0; // We don't check last index as it is considered as winning move
+    }
+
+    static boolean canMoveBackward(int index, int[] game) {
+        return index > 0 && game[index - 1] == 0;
+    }
+
+    static boolean canJump(int index, int leap, int[] game) {
+        return game[index + leap] == 0; // We don't bother here about index overflow too
+    }
+
+    private static boolean move(int index, int leap, int[] game, int[] history) {
+        if (Arrays.stream(history).anyMatch(i -> i == index)) {
+            return false;
+        }
+        var newHistory = Arrays.copyOf(history, history.length + 1);
+        newHistory[newHistory.length - 1] = index;
+        if (isWinningMove(index, leap, game.length)) {
+            return true;
+        }
+        if (canMoveForward(index, game) && move(index + 1, leap, game, newHistory)) {
+            return true;
+        }
+        if (canJump(index, leap, game) && move(index + leap, leap, game, newHistory)) {
+            return true;
+        }
+        return canMoveBackward(index, game) && move(index - 1, leap, game, newHistory);
+    }
+
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+        int q = scan.nextInt();
+        while (q-- > 0) {
+            int n = scan.nextInt();
+            int leap = scan.nextInt();
+
+            int[] game = new int[n];
+            for (int i = 0; i < n; i++) {
+                game[i] = scan.nextInt();
+            }
+
+            System.out.println((canWin(leap, game)) ? "YES" : "NO");
+        }
+        scan.close();
+    }
+
+}
diff --git a/src/test/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/SolutionTest.java b/src/test/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/SolutionTest.java
new file mode 100644
index 0000000..542511a
--- /dev/null
+++ b/src/test/java/eu/ztsh/training/hackerrank/datastructures/array_1d_pt2/SolutionTest.java
@@ -0,0 +1,83 @@
+package eu.ztsh.training.hackerrank.datastructures.array_1d_pt2;
+
+import java.util.List;
+import eu.ztsh.training.hackerrank.HackerRankTest;
+import eu.ztsh.training.hackerrank.SolutionClassDescription;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SolutionTest extends HackerRankTest {
+
+    @Override
+    protected SolutionClassDescription getSolutionClassDescription() {
+        return new SolutionClassDescription(Solution.class);
+    }
+
+    @Nested
+    @DisplayName("Provided test cases")
+    class TestCases {
+
+        @Test
+        public void testCase0() {
+            simpleAssert(
+                    List.of(
+                            "4",
+                            "5 3",
+                            "0 0 0 0 0",
+                            "6 5",
+                            "0 0 0 1 1 1",
+                            "6 3",
+                            "0 0 1 1 1 0",
+                            "3 1",
+                            "0 1 0"
+                    ),
+                    List.of(
+                            "YES",
+                            "YES",
+                            "NO",
+                            "NO"
+                    )
+            );
+        }
+
+    }
+
+    @Nested
+    @DisplayName("Unit tests")
+    class UnitTests {
+
+        @Test
+        public void winningMoveTest() {
+            assertThat(Solution.isWinningMove(0, 1, 2)).isFalse();
+            assertThat(Solution.isWinningMove(1, 5, 6)).isTrue();
+        }
+
+        @Test
+        public void moveForwardTest() {
+            var game = new int[]{0, 0, 1};
+            assertThat(Solution.canMoveForward(0, game)).isTrue();
+            assertThat(Solution.canMoveForward(1, game)).isFalse();
+        }
+
+        @Test
+        public void moveBackwardTest() {
+            var game = new int[]{0, 1, 0, 0, 1};
+            assertThat(Solution.canMoveBackward(0, game)).isFalse();
+            assertThat(Solution.canMoveBackward(3, game)).isTrue();
+            assertThat(Solution.canMoveBackward(2, game)).isFalse();
+        }
+
+        @Test
+        public void jumpTest() {
+            var game = new int[]{0, 0, 1, 1, 1, 0};
+            assertThat(Solution.canJump(0, 3, game)).isFalse();
+            assertThat(Solution.canJump(1, 3, game)).isFalse();
+            assertThat(Solution.canJump(1, 4, game)).isTrue();
+        }
+
+    }
+
+}
\ No newline at end of file