Merge pull request #4 from marcode24/challenges

feat: add number in expanded form solution

Author: marcode24

codewars/number-in-expanded-form/README.md

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+# Write Number in Expanded Form
+
+## Description
+
+You will be given a number and you will need to return it as a string in Expanded Form. For example:
+
+```js
+expandedForm(12); // should return '10 + 2'
+expandedForm(42); // should return '40 + 2'
+expandedForm(70304); // should return '70000 + 300 + 4'
+```
+
+**NOTE:** All numbers will be whole numbers greater than 0.

codewars/number-in-expanded-form/solution.js

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+const expandedForm = (num) => {
+  num = num.toString().split('').reverse();
+  const results = [];
+  num.forEach((item, index) => {
+    if (item !== '0') {
+      results.push(`${item}${'0'.repeat(index)}`);
+    }
+  });
+  return results.reverse().join(' + ');
+};
+
+module.exports = expandedForm;

codewars/number-in-expanded-form/solution.test.js

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+const expandedForm = require('./solution');
+
+describe('Number in expanded form', () => {
+  const testCases = [
+    {
+      input: 12,
+      output: '10 + 2',
+    },
+    {
+      input: 42,
+      output: '40 + 2',
+    },
+    {
+      input: 70304,
+      output: '70000 + 300 + 4',
+    },
+    {
+      input: 10345354,
+      output: '10000000 + 300000 + 40000 + 5000 + 300 + 50 + 4',
+    },
+  ];
+
+  it('should return a string type', () => {
+    expect(typeof expandedForm(12)).toBe('string');
+  });
+
+  it.each(testCases)('should return the correct output', ({ input, output }) => {
+    expect(expandedForm(input)).toBe(output);
+  });
+});

codewars/range-extraction/README.md

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+# Range Extraction
+
+## Description
+
+A format for expressing an ordered list of integers is to use a comma separated list of either
+
+- individual integers
+- or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. The range includes all integers in the interval including both endpoints. It is not considered a range unless it spans at least 3 numbers. For example "12,13,15-17"
+
+Complete the solution so that it takes a list of integers in increasing order and returns a correctly formatted string in the range format.
+
+Example:
+
+```js
+solution([
+  -10, -9, -8, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18,
+  19, 20,
+]);
+// returns "-10--8,-6,-3-1,3-5,7-11,14,15,17-20"
+```

codewars/range-extraction/solution.js

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+const solution = (list) => {
+  let result = '';
+  let start = list[0];
+  let end = list[0];
+  let i = 1;
+
+  while (i < list.length) {
+    if (list[i] - list[i - 1] === 1) {
+      end = list[i];
+    } else {
+      if (start === end) {
+        result += `${start},`;
+      } else if (end - start === 1) {
+        result += `${start},${end},`;
+      } else {
+        result += `${start}-${end},`;
+      }
+      start = list[i];
+      end = list[i];
+    }
+    i += 1;
+  }
+  if (start === end) {
+    result += `${start}`;
+  } else if (end - start === 1) {
+    result += `${start},${end}`;
+  } else {
+    result += `${start}-${end}`;
+  }
+
+  return result;
+};
+
+module.exports = solution;

codewars/range-extraction/solution.test.js

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+const solution = require('./solution');
+
+describe('Range extraction', () => {
+  const testCases = [
+    {
+      input: [-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20],
+      output: '-6,-3-1,3-5,7-11,14,15,17-20',
+    },
+    {
+      input: [-3, -2, -1, 2, 10, 15, 16, 18, 19, 20],
+      output: '-3--1,2,10,15,16,18-20',
+    },
+    {
+      input: [-10, -9, -8, -6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17,
+        18, 19, 20],
+      output: '-10--8,-6,-3-1,3-5,7-11,14,15,17-20',
+    },
+    {
+      input: [-3, -2, -1, 2, 10, 15, 16, 18, 19, 20, 22, 23],
+      output: '-3--1,2,10,15,16,18-20,22,23',
+    },
+  ];
+
+  it('should return a string', () => {
+    expect(typeof solution([-1, 0, 1, 2, 6, 7, 9])).toBe('string');
+  });
+
+  it.each(testCases)('should return the correct output', (testCase) => {
+    expect(solution(testCase.input)).toBe(testCase.output);
+  });
+});

codewars/roman-numerals-encoder/README.md

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+# Roman Numerals Encoder
+
+## Description
+
+Create a function taking a positive integer between 1 and 3999 (both included) as its parameter and returning a string containing the Roman Numeral representation of that integer.
+
+Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.
+
+Example:
+
+```js
+solution(1000); // should return 'M'
+```
+
+Help:
+
+```txt
+Symbol Value
+I 1
+V 5
+X 10
+L 50
+C 100
+D 500
+M 1,000
+```
+
+Remember that there can't be more than 3 identical symbols in a row.

codewars/roman-numerals-encoder/solution.js

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+const solution = (number) => {
+  const romanNumerals = {
+    1: 'I',
+    4: 'IV',
+    5: 'V',
+    9: 'IX',
+    10: 'X',
+    40: 'XL',
+    50: 'L',
+    90: 'XC',
+    100: 'C',
+    400: 'CD',
+    500: 'D',
+    900: 'CM',
+    1000: 'M',
+  };
+
+  const romanNumeralsKeys = Object.keys(romanNumerals).reverse();
+  let result = '';
+
+  Array.from({ length: romanNumeralsKeys.length }).forEach((_, i) => {
+    const key = romanNumeralsKeys[i];
+    const value = romanNumerals[key];
+    while (number >= key) {
+      result += value;
+      number -= key;
+    }
+  });
+
+  return result;
+};
+
+module.exports = solution;

codewars/roman-numerals-encoder/solution.test.js

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+const solution = require('./solution');
+
+describe('Roman Numerals Encoder', () => {
+  const testCases = [
+    {
+      input: 1,
+      output: 'I',
+    },
+    {
+      input: 2,
+      output: 'II',
+    },
+    {
+      input: 3,
+      output: 'III',
+    },
+    {
+      input: 4,
+      output: 'IV',
+    },
+    {
+      input: 5,
+      output: 'V',
+    },
+    {
+      input: 9,
+      output: 'IX',
+    },
+    {
+      input: 10,
+      output: 'X',
+    },
+    {
+      input: 11,
+      output: 'XI',
+    },
+    {
+      input: 19,
+      output: 'XIX',
+    },
+    {
+      input: 22,
+      output: 'XXII',
+    },
+    {
+      input: 15,
+      output: 'XV',
+    },
+    {
+      input: 1000,
+      output: 'M',
+    },
+    {
+      input: 1001,
+      output: 'MI',
+    },
+    {
+      input: 1990,
+      output: 'MCMXC',
+    },
+    {
+      input: 2007,
+      output: 'MMVII',
+    },
+    {
+      input: 2008,
+      output: 'MMVIII',
+    },
+  ];
+
+  it('should return a string type', () => {
+    expect(solution(1)).toBe('I');
+  });
+
+  it.each(testCases)('should return $output', (testCase) => {
+    expect(solution(testCase.input)).toBe(testCase.output);
+  });
+});

codewars/what-century-is-it/README.md

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+# What Century Is It?
+
+## Description
+
+Return the century of the input year. The input will always be a 4 digit string, so there is no need for validation.
+
+Examples
+
+```txt
+"1999" --> "20th"
+"2011" --> "21st"
+"2154" --> "22nd"
+"2259" --> "23rd"
+"1124" --> "12th"
+"2000" --> "20th"
+```