Binary search

typescript/binary-search/.eslintignore

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+!.meta
+
+# Protected or generated
+.git
+.vscode
+
+# When using npm
+node_modules/*
+
+# Configuration files
+.eslintrc.cjs
+babel.config.cjs
+jest.config.cjs

typescript/binary-search/.eslintrc.cjs

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+module.exports = {
+  root: true,
+  parserOptions: {
+    tsconfigRootDir: __dirname,
+    project: ['./tsconfig.json'],
+  },
+  overrides: [
+    // Student provided files
+    {
+      files: ['*.ts'],
+      excludedFiles: ['.meta/proof.ci.ts', '.meta/exemplar.ts', '*.test.ts'],
+      extends: '@exercism/eslint-config-typescript',
+    },
+    // Exercism given tests
+    {
+      files: ['*.test.ts'],
+      excludedFiles: ['custom.test.ts'],
+      env: {
+        jest: true,
+      },
+      extends: '@exercism/eslint-config-typescript/maintainers',
+    },
+    // Student provided tests
+    {
+      files: ['custom.test.ts'],
+      env: {
+        jest: true,
+      },
+      extends: '@exercism/eslint-config-typescript',
+    },
+    // Exercism provided files
+    {
+      files: ['.meta/proof.ci.ts', '.meta/exemplar.ts', '*.test.ts'],
+      excludedFiles: ['custom.test.ts'],
+      extends: '@exercism/eslint-config-typescript/maintainers',
+      rules: {
+        "@typescript-eslint/semi": 0,
+      },
+    },
+  ],
+}

typescript/binary-search/.exercism/config.json

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+{
+  "blurb": "Implement a binary search algorithm.",
+  "authors": ["anuragsoni"],
+  "contributors": ["masters3d", "SleeplessByte"],
+  "files": {
+    "solution": ["binary-search.ts"],
+    "test": ["binary-search.test.ts"],
+    "example": [".meta/proof.ci.ts"]
+  },
+  "source": "Wikipedia",
+  "source_url": "http://en.wikipedia.org/wiki/Binary_search_algorithm"
+}

typescript/binary-search/.exercism/metadata.json

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+{"track":"typescript","exercise":"binary-search","id":"5cf2bca8a7db47c6ab347c24290b25dd","url":"https://exercism.org/tracks/typescript/exercises/binary-search","handle":"briemens","is_requester":true,"auto_approve":false}

typescript/binary-search/HELP.md

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+# Help
+
+## Running the tests
+
+Execute the tests with:
+
+```bash
+$ yarn test
+```
+
+## Skipped tests
+
+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 `xit` to
+`it`.
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit binary-search.ts` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [TypeScript track's documentation](https://exercism.org/docs/tracks/typescript)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [TypeScript QuickStart](https://www.typescriptlang.org/docs/handbook/release-notes/overview.html)
+- [ECMAScript 2015 Language Specification](https://www.ecma-international.org/wp-content/uploads/ECMA-262_6th_edition_june_2015.pdf) (pdf)
+- [Mozilla JavaScript Reference](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference)
+- [/r/typescript](https://www.reddit.com/r/typescript) is the TypeScript subreddit.
+- [StackOverflow](https://stackoverflow.com/questions/tagged/typescript) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

typescript/binary-search/README.md

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+# Binary Search
+
+Welcome to Binary Search on Exercism's TypeScript Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Implement a binary search algorithm.
+
+Searching a sorted collection is a common task. A dictionary is a sorted
+list of word definitions. Given a word, one can find its definition. A
+telephone book is a sorted list of people's names, addresses, and
+telephone numbers. Knowing someone's name allows one to quickly find
+their telephone number and address.
+
+If the list to be searched contains more than a few items (a dozen, say)
+a binary search will require far fewer comparisons than a linear search,
+but it imposes the requirement that the list be sorted.
+
+In computer science, a binary search or half-interval search algorithm
+finds the position of a specified input value (the search "key") within
+an array sorted by key value.
+
+In each step, the algorithm compares the search key value with the key
+value of the middle element of the array.
+
+If the keys match, then a matching element has been found and its index,
+or position, is returned.
+
+Otherwise, if the search key is less than the middle element's key, then
+the algorithm repeats its action on the sub-array to the left of the
+middle element or, if the search key is greater, on the sub-array to the
+right.
+
+If the remaining array to be searched is empty, then the key cannot be
+found in the array and a special "not found" indication is returned.
+
+A binary search halves the number of items to check with each iteration,
+so locating an item (or determining its absence) takes logarithmic time.
+A binary search is a dichotomic divide and conquer search algorithm.
+
+## Source
+
+### Created by
+
+- @anuragsoni
+
+### Contributed to by
+
+- @masters3d
+- @SleeplessByte
+
+### Based on
+
+Wikipedia - http://en.wikipedia.org/wiki/Binary_search_algorithm

typescript/binary-search/babel.config.cjs

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+module.exports = {
+  presets: ['@exercism/babel-preset-typescript'],
+  plugins: [],
+}

typescript/binary-search/binary-search.test.ts

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+import { find } from "./binary-search";
+
+describe("Binary Search", () => {
+  it("finds a value in an array with one element", () => {
+    expect(find([6], 6)).toEqual(0);
+  });
+
+  it("finds a value in the middle of an array", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(find(array, 6)).toEqual(3);
+  });
+
+  it("finds a value at the beginning of an array", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(find(array, 1)).toEqual(0);
+  });
+
+  it("finds a value at the end of an array", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(find(array, 11)).toEqual(6);
+  });
+
+  it("finds a value in an array of odd length", () => {
+    const array = [1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 634];
+    expect(find(array, 144)).toEqual(9);
+  });
+
+  it("finds a value in an array of even length", () => {
+    const array = [1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377];
+    expect(find(array, 21)).toEqual(5);
+  });
+
+  it("identifies that a value is not included in the array", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(() => find(array, 7)).toThrow(new Error("Value not in array"));
+  });
+
+  it("a value smaller than the array's smallest value is not found", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(() => find(array, 0)).toThrow(new Error("Value not in array"));
+  });
+
+  it("a value larger than the array's largest value is not found", () => {
+    const array = [1, 3, 4, 6, 8, 9, 11];
+    expect(() => find(array, 13)).toThrow(new Error("Value not in array"));
+  });
+
+  it("nothing is found in an empty array", () => {
+    expect(() => find([], 1)).toThrow(new Error("Value not in array"));
+  });
+
+  it("nothing is found when the left and right bounds cross", () => {
+    expect(() => find([1, 2], 0)).toThrow(new Error("Value not in array"));
+  });
+});

typescript/binary-search/binary-search.ts

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+export function find(
+  haystack: number[],
+  needle: number,
+  start: number = 0,
+  end: number = haystack.length - 1
+): number | never {
+  if (start > end || end < start) {
+    throw new Error("Value not in array");
+  }
+  const index = start + Math.floor((end - start) / 2);
+  const value = haystack[index];
+  if (needle > value) {
+    return find(haystack, needle, index + 1, end);
+  }
+  if (needle < value) {
+    return find(haystack, needle, start, index - 1);
+  }
+  return index;
+}

typescript/binary-search/jest.config.cjs

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+module.exports = {
+  verbose: true,
+  projects: ['<rootDir>'],
+  testMatch: [
+    '**/__tests__/**/*.[jt]s?(x)',
+    '**/test/**/*.[jt]s?(x)',
+    '**/?(*.)+(spec|test).[jt]s?(x)',
+  ],
+  testPathIgnorePatterns: [
+    '/(?:production_)?node_modules/',
+    '.d.ts$',
+    '<rootDir>/test/fixtures',
+    '<rootDir>/test/helpers',
+    '__mocks__',
+  ],
+  transform: {
+    '^.+\\.[jt]sx?$': 'babel-jest',
+  },
+}

typescript/binary-search/package.json

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+{
+  "name": "@exercism/typescript-binary-search",
+  "version": "1.0.0",
+  "description": "Exercism exercises in Typescript.",
+  "private": true,
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/exercism/typescript"
+  },
+  "type": "module",
+  "engines": {
+    "node": "^14.13.1 || >=16.0.0"
+  },
+  "devDependencies": {
+    "@exercism/babel-preset-typescript": "^0.1.0",
+    "@exercism/eslint-config-typescript": "^0.4.1",
+    "@types/jest": "^27.4.0",
+    "@types/node": "^16.11.24",
+    "babel-jest": "^27.5.1",
+    "core-js": "^3.21.0",
+    "eslint": "^8.9.0",
+    "jest": "^27.5.1",
+    "typescript": "^4.5.4"
+  },
+  "scripts": {
+    "test": "yarn lint:types && jest --no-cache",
+    "lint": "yarn lint:types && yarn lint:ci",
+    "lint:types": "yarn tsc --noEmit -p .",
+    "lint:ci": "eslint . --ext .tsx,.ts"
+  }
+}

typescript/binary-search/tsconfig.json

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+{
+  "display": "Configuration for Exercism TypeScript Exercises",
+  "compilerOptions": {
+    // Allows you to use the newest syntax, and have access to console.log
+    // https://www.typescriptlang.org/tsconfig#lib
+    "lib": ["ESNEXT", "dom"],
+    // Make sure typescript is configured to output ESM
+    // https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c#how-can-i-make-my-typescript-project-output-esm
+    "module": "ES2020",
+    // Since this project is using babel, TypeScript may target something very
+    // high, and babel will make sure it runs on your local Node version.
+    // https://babeljs.io/docs/en/
+    "target": "ESNext", // ESLint doesn't support this yet: "es2022",
+
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+
+    // Because we'll be using babel: ensure that Babel can safely transpile
+    // files in the TypeScript project.
+    //
+    // https://babeljs.io/docs/en/babel-plugin-transform-typescript/#caveats
+    "isolatedModules": true
+  },
+  "include": ["*.ts", "*.tsx", ".meta/*.ts", ".meta/*.tsx"],
+  "exclude": ["node_modules"]
+}