javascript - queen-attack

javascript/queen-attack/README.md

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+# Queen Attack
+
+Given the position of two queens on a chess board, indicate whether or not they
+are positioned so that they can attack each other.
+
+In the game of chess, a queen can attack pieces which are on the same
+row, column, or diagonal.
+
+A chessboard can be represented by an 8 by 8 array.
+
+So if you're told the white queen is at (2, 3) and the black queen at
+(5, 6), then you'd know you've got a set-up like so:
+
+```text
+_ _ _ _ _ _ _ _
+_ _ _ _ _ _ _ _
+_ _ _ W _ _ _ _
+_ _ _ _ _ _ _ _
+_ _ _ _ _ _ _ _
+_ _ _ _ _ _ B _
+_ _ _ _ _ _ _ _
+_ _ _ _ _ _ _ _
+```
+
+You'd also be able to answer whether the queens can attack each other.
+In this case, that answer would be yes, they can, because both pieces
+share a diagonal.
+
+## Setup
+
+Go through the setup instructions for Javascript to
+install the necessary dependencies:
+
+[https://exercism.io/tracks/javascript/installation](https://exercism.io/tracks/javascript/installation)
+
+## Requirements
+
+Install assignment dependencies:
+
+```bash
+$ npm install
+```
+
+## Making the test suite pass
+
+Execute the tests with:
+
+```bash
+$ npm test
+```
+
+In the test suites all tests but the first have been skipped.
+
+Once you get a test passing, you can enable the next one by
+changing `xtest` to `test`.
+
+
+## Source
+
+J Dalbey's Programming Practice problems [http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html](http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

javascript/queen-attack/package.json

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+{
+  "name": "exercism-javascript",
+  "version": "0.0.0",
+  "description": "Exercism exercises in Javascript.",
+  "author": "Katrina Owen",
+  "private": true,
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/exercism/javascript"
+  },
+  "devDependencies": {
+    "babel-jest": "^21.2.0",
+    "babel-plugin-transform-builtin-extend": "^1.1.2",
+    "babel-preset-env": "^1.4.0",
+    "eslint": "^3.19.0",
+    "eslint-config-airbnb": "^15.0.1",
+    "eslint-plugin-import": "^2.2.0",
+    "eslint-plugin-jsx-a11y": "^5.0.1",
+    "eslint-plugin-react": "^7.0.1",
+    "jest": "^21.2.1"
+  },
+  "jest": {
+    "modulePathIgnorePatterns": [
+      "package.json"
+    ]
+  },
+  "babel": {
+    "presets": [
+      [
+        "env",
+        {
+          "targets": [
+            {
+              "node": "current"
+            }
+          ]
+        }
+      ]
+    ],
+    "plugins": [
+      [
+        "babel-plugin-transform-builtin-extend",
+        {
+          "globals": [
+            "Error"
+          ]
+        }
+      ],
+      [
+        "transform-regenerator"
+      ]
+    ]
+  },
+  "scripts": {
+    "test": "jest --no-cache ./*",
+    "watch": "jest --no-cache --watch ./*",
+    "lint": "eslint .",
+    "lint-test": "eslint . && jest --no-cache ./* "
+  },
+  "eslintConfig": {
+    "parserOptions": {
+      "ecmaVersion": 6,
+      "sourceType": "module"
+    },
+    "env": {
+      "es6": true,
+      "node": true,
+      "jest": true
+    },
+    "extends": "airbnb",
+    "rules": {
+      "import/no-unresolved": "off",
+      "import/extensions": "off"
+    }
+  },
+  "licenses": [
+    "MIT"
+  ],
+  "dependencies": {}
+}

javascript/queen-attack/queen-attack.js

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+const GRID_SIZE = 8;
+
+export default class Queens {
+
+  constructor(defaultPositions = {}) {
+    this.setPosition('white', defaultPositions.white || [0, 3]);
+    this.setPosition('black', defaultPositions.black || [7, 3]);
+  }
+
+  toString() {
+    let board = [];
+    for (let x = 0; x < GRID_SIZE; x += 1) {
+      const row = [];
+      for (let y = 0; y < GRID_SIZE; y += 1) {
+        if (Queens.isEqual(this.white, [x, y])) {
+          row.push('W');
+        } else if (Queens.isEqual(this.black, [x, y])) {
+          row.push('B');
+        } else {
+          row.push('_');
+        }
+      }
+      board += `${row.join(' ')}\n`;
+    }
+    return board;
+  }
+
+  canAttack() {
+    if (this.white[0] === this.black[0]) {
+      return true; // Same Row
+    } else if (this.white[1] === this.black[1]) {
+      return true; // Same Column
+    } else if ((Math.abs(this.white[0] - this.black[0])) ===
+               (Math.abs(this.white[1] - this.black[1]))) {
+      return true; // On a diagonal
+    }
+    return false;
+  }
+
+  setPosition(color, position) {
+    if (Queens.isEqual(position, this.getOpponentPosition(color))) {
+      throw Error('Queens cannot share the same space');
+    }
+
+    this[color] = position;
+  }
+
+  getOpponentPosition(color) {
+    return (color === 'white') ? this.black : this.white;
+  }
+
+  static isEqual(pos1, pos2) {
+    return JSON.stringify(pos1) === JSON.stringify(pos2);
+  }
+}

javascript/queen-attack/queen-attack.spec.js

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+import Queens from './queen-attack';
+
+describe('Queens', () => {
+  test('has the correct default positions', () => {
+    const queens = new Queens();
+    expect(queens.white).toEqual([0, 3]);
+    expect(queens.black).toEqual([7, 3]);
+  });
+
+  test('initialized with specific placement', () => {
+    const queens = new Queens({ white: [3, 7], black: [6, 1] });
+    expect(queens.white).toEqual([3, 7]);
+    expect(queens.black).toEqual([6, 1]);
+  });
+
+  test('cannot occupy the same space', () => {
+    const positioning = { white: [2, 4], black: [2, 4] };
+    const expectedError = 'Queens cannot share the same space';
+    expect(() => new Queens(positioning)).toThrow(expectedError);
+  });
+
+  test('toString representation', () => {
+    const positioning = { white: [2, 4], black: [6, 6] };
+    const queens = new Queens(positioning);
+    const board = ['_ _ _ _ _ _ _ _',
+      '_ _ _ _ _ _ _ _',
+      '_ _ _ _ W _ _ _',
+      '_ _ _ _ _ _ _ _',
+      '_ _ _ _ _ _ _ _',
+      '_ _ _ _ _ _ _ _',
+      '_ _ _ _ _ _ B _',
+      '_ _ _ _ _ _ _ _\n'].join('\n');
+    expect(queens.toString()).toEqual(board);
+  });
+
+  test('queens cannot attack', () => {
+    const queens = new Queens({ white: [2, 3], black: [4, 7] });
+    expect(queens.canAttack()).toEqual(false);
+  });
+
+  test('queens can attack when they are on the same row', () => {
+    const queens = new Queens({ white: [2, 4], black: [2, 7] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack when they are on the same column', () => {
+    const queens = new Queens({ white: [5, 4], black: [2, 4] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack diagonally', () => {
+    const queens = new Queens({ white: [1, 1], black: [6, 6] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack another diagonally', () => {
+    const queens = new Queens({ white: [0, 6], black: [1, 7] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack yet another diagonally', () => {
+    const queens = new Queens({ white: [4, 1], black: [6, 3] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack on a north-east/south-west diagonal', () => {
+    const queens = new Queens({ white: [7, 0], black: [0, 7] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+
+  test('queens can attack on another ne/sw diagonal', () => {
+    const queens = new Queens({ white: [2, 6], black: [5, 3] });
+    expect(queens.canAttack()).toEqual(true);
+  });
+});