feat: kata/pong-basics

kata/6-kyu/index.md

@@ -271,6 +271,7 @@
 - [+1 Array](plus-1-array "5514e5b77e6b2f38e0000ca9")
 - [Points in the circle](points-in-the-circle "5b55c49d4a317adff500015f")
 - [Polybius square cipher - encode](polybius-square-cipher-encode "542a823c909c97da4500055e")
+- [Pong! [Basics]](pong-basics "5b432bdf82417e3f39000195")
 - [Positions Average](positions-average "59f4a0acbee84576800000af")
 - [Possibilities of throwing a coin n times](possibilities-of-throwing-a-coin-n-times "5ad6266b673f2f067b000004")
 - [Prime factorization](prime-factorization "534a0c100d03ad9772000539")

kata/6-kyu/pong-basics/README.md

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+# [Pong! [Basics]](https://www.codewars.com/kata/pong-basics "https://www.codewars.com/kata/5b432bdf82417e3f39000195")
+
+You must finish the `Pong` class. It has a constructor which accepts the `maximum score` a player can get throughout the game, and a method
+called `play`. This method determines whether the current player hit the ball or not, i.e. if the paddle is at the sufficient height to hit
+it back. There are 4 possible outcomes: player successfully hits the ball back, player misses the ball, player misses the ball **and his
+opponent reaches the maximum score winning the game**, either player tries to hit a ball despite the game being over. You can see the input
+and output description in detail below.
+
+### "Play" method input:
+
+* ball position - The Y coordinate of the ball
+* player position - The Y coordinate of the centre(!) of the current player's paddle
+
+### "Play" method output:
+
+One of the following strings:
+
+* `"Player X has hit the ball!"` - If the ball "hits" the paddle
+* `"Player X has missed the ball!"` - If the ball is above/below the paddle
+* `"Player X has won the game!"` - If one of the players has reached the maximum score
+* `"Game Over!"` - If the game has ended when the `play` method is called
+
+### Important notes:
+
+* Players take turns hitting the ball, always starting the game with the Player 1.
+* The paddles are `7` pixels in height.
+* The ball is `1` pixel in height.
+
+___
+
+## Example
+
+```
+let game = new Pong(2); // Here we say that the score to win is 2
+game.play(50, 53)
+->
+"Player 1 has hit the ball!"; // Player 1 hits the ball
+game.play(100, 97)
+->
+"Player 2 has hit the ball!"; // Player 2 hits it back
+game.play(0, 4)
+->
+"Player 1 has missed the ball!"; // Player 1 misses so Player 2 gains a point
+game.play(25, 25)
+->
+"Player 2 has hit the ball!"; // Player 2 hits the ball
+game.play(75, 25)
+->
+"Player 2 has won the game!"; // Player 1 misses again. Having 2 points Player 2 wins, so we return the corresponding string
+game.play(50, 50)
+->
+"Game Over!"; // Another turn is made even though the game is already over
+```

kata/6-kyu/pong-basics/main/Pong.java

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+class Pong {
+  private final int[] scores = new int[2];
+  private final int maxScore;
+  private int player;
+
+  Pong(int maxScore) {
+    this.maxScore = maxScore;
+  }
+
+  String play(int ballPos, int playerPos) {
+    if (scores[0] == maxScore || scores[1] == maxScore) {
+      return "Game Over!";
+    }
+    player ^= 1;
+    boolean hit = Math.abs(ballPos - playerPos) < 4;
+    if (hit || ++scores[player] < maxScore) {
+      return String.format("Player %d has %s the ball!", 2 - player, hit ? "hit" : "missed");
+    }
+    return String.format("Player %d has won the game!", player + 1);
+  }
+}

kata/6-kyu/pong-basics/test/SolutionTest.java

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+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+  @Test
+  void player1() {
+    Pong game = new Pong(1);
+    assertEquals("Player 1 has hit the ball!", game.play(360, 363));
+    assertEquals("Player 1 has won the game!", game.play(575, 582));
+    assertEquals("Game Over!", game.play(-1, -1));
+  }
+
+  @Test
+  void player2() {
+    Pong game = new Pong(2);
+    assertEquals("Player 1 has hit the ball!", game.play(50, 53));
+    assertEquals("Player 2 has hit the ball!", game.play(100, 97));
+    assertEquals("Player 1 has missed the ball!", game.play(0, 4));
+    assertEquals("Player 2 has hit the ball!", game.play(25, 25));
+    assertEquals("Player 2 has won the game!", game.play(75, 25));
+    assertEquals("Game Over!", game.play(50, 50));
+  }
+}