implement Connect4 challenge

technical-fundamentals/coding/__tests__/connect4.test.mjs

@@ -1,12 +1,12 @@
-import { describe, it, expect, vi } from "vitest";
-import { Connect4, PLAYER_ONE, PLAYER_TWO } from "../connect4.mjs";
+import { describe, it, expect } from "vitest";
+import { Connect4, PLAYER_ONE } from "../connect4.mjs";
 
 describe("Connect4", () => {
   it("It should allow you play within bounds", async () => {
     const c4 = new Connect4({ width: 10, height: 10 });
-    expect(c4.getValue(10, 1)).toBeFalsy();
+    expect(c4.getValue(9, 1)).toBeFalsy();
     c4.play(1);
-    expect(c4.getValue(10, 1)).toEqual(PLAYER_ONE);
+    expect(c4.getValue(9, 1)).toEqual(PLAYER_ONE);
   });
 
   it("It should do nothing if you play out of bounds", async () => {
@@ -33,14 +33,14 @@ describe("Connect4", () => {
     expect(c4.winner()).toEqual(PLAYER_ONE);
   });
 
-  it("it should detect diagonal winning", () => {
+  it("it should detect diagonal winning right", () => {
     const c4 = new Connect4({ width: 10, height: 10 });
     const plays = [1, 2, 2, 3, 4, 3, 3, 4, 5, 4, 4];
     plays.forEach((p) => c4.play(p));
     expect(c4.winner()).toEqual(PLAYER_ONE);
   });
 
-  it("it should detect diagonal winning", () => {
+  it("it should detect diagonal winning left", () => {
     const c4 = new Connect4({ width: 10, height: 10 });
     const plays = [1, 2, 2, 3, 4, 3, 3, 4, 5, 4, 4].reverse();
     plays.forEach((p) => c4.play(p));

technical-fundamentals/coding/connect4.mjs

@@ -1,20 +1,131 @@
 /**
-Connect4
+ Connect4
 
-Connect4 is a game where two players take turns placing a token on columns that drop to the bottom.
-When a player forms 4 of his tokens in a line - horizontally, vertically,or diagonally - the player wins.
+ Connect4 is a game where two players take turns placing a token on columns that drop to the bottom.
+ When a player forms 4 of his tokens in a line - horizontally, vertically,or diagonally - the player wins.
 
-[Visualization](https://i.ebayimg.com/images/g/DzMAAOSwSjxj6m0e/s-l1600.jpg)
+ [Visualization](https://i.ebayimg.com/images/g/DzMAAOSwSjxj6m0e/s-l1600.jpg)
 
-Implement Connect 4 with the class below.
-*/
+ Implement Connect 4 with the class below.
+ */
 
 export const PLAYER_ONE = 1;
 export const PLAYER_TWO = 2;
 
 export class Connect4 {
-  constructor() {}
-  play(col) {}
-  checkWinner() {}
+  board = [];
+  currentPlayer;
+  theWinner;
+  constructor() {
+    this.board = Array.from({length: 10}, () => Array(10).fill(0));
+    this.currentPlayer = PLAYER_ONE;
+  }
+  play(col) {
+
+    if (this.theWinner) return;
+
+    for (let row=this.board.length - 1; row>=0; row--) {
+      if (this.board[row][col] === 0) {
+        this.board[row][col] = this.currentPlayer;
+        this.checkWinner(row, col);
+        break;
+      }
+    }
+
+    this.currentPlayer = this.currentPlayer === PLAYER_ONE ? PLAYER_TWO : PLAYER_ONE;
+
+  }
+
+  getValue(row, col) {
+    if (row<0 || col<0 || row>this.board.length - 1 || col>this.board[0].length) {
+      return false;
+    }
+
+    return this.board[row][col];
+  }
+  checkWinner(row, col) {
+
+    const height = this.board.length;
+    const width = this.board[0].length;
+
+    const checkFour = (self, count) => {
+      if (count >= 4) {
+        self.theWinner = self.currentPlayer;
+        return true;
+      }
+    }
+
+    let count = 0;
+    //vertically bottom
+    let y = row;
+    while (y<=height - 1 && this.currentPlayer === this.board[y][col]) {
+      y++;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+
+    //horizontally left
+    count = 0;
+    let x = col;
+    while (x>=0 && this.currentPlayer === this.board[row][x]) {
+      x--;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+    //horizontally right
+    x = col+1;
+    while (x<=width && this.currentPlayer === this.board[row][x]) {
+      x++;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+
+    // diagonally left top
+    count = 0;
+    x = col;
+    y = row;
+    while (x>=0 && y>=0 && this.currentPlayer === this.board[y][x]) {
+      x--;
+      y--;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+
+    // diagonally right bottom
+    x = col+1;
+    y = row+1;
+    while (x<=width - 1 && y<=height - 1 && this.currentPlayer === this.board[y][x]) {
+      x++;
+      y++;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+
+    // diagonally right top
+    count = 0;
+    x = col;
+    y = row;
+    while (x<=width - 1 && y>=0 && this.currentPlayer === this.board[y][x]) {
+      x++;
+      y--;
+      count++;
+    }
+    if (checkFour(this, count)) return;
+
+    // diagonally left bottom
+    x = col-1;
+    y = row+1;
+    while (x>=0 && y<=height - 1 && this.currentPlayer === this.board[y][x]) {
+      x--;
+      y++;
+      count++;
+    }
+    checkFour(this, count);
+
+  }
   print() {}
+
+  winner() {
+    return this.theWinner;
+  }
 }