Birmingham | 26 JAN ITP | Merve Reis | Sprint 1 | Data Groups

Sprint-1/fix/median.js

@@ -5,10 +5,35 @@
 // Hint: Please consider scenarios when 'list' doesn't have numbers (the function is expected to return null)
 // or 'list' has mixed values (the function is expected to sort only numbers).
 
+// function calculateMedian(list) {
+//   const middleIndex = Math.floor(list.length / 2);
+//   const median = list.splice(middleIndex, 1)[0];
+//   return median;
+// }
+
+// module.exports = calculateMedian;
+
 function calculateMedian(list) {
-  const middleIndex = Math.floor(list.length / 2);
-  const median = list.splice(middleIndex, 1)[0];
-  return median;
+  if (!Array.isArray(list) || list.length === 0) {
+    return null;
+  }
+
+  const numbers = list.filter((item) => Number.isFinite(item));
+
+  if (numbers.length === 0) {
+    return null;
+  }
+
+  // Copy before sort (extra safety, though filter already creates new array)
+  const sorted = [...numbers].sort((a, b) => a - b);
+
+  const middle = Math.floor(sorted.length / 2);
+
+  if (sorted.length % 2 === 0) {
+    return (sorted[middle - 1] + sorted[middle]) / 2;
+  }
+
+  return sorted[middle];
 }
 
 module.exports = calculateMedian;

Sprint-1/fix/median.test.js

@@ -13,7 +13,8 @@ describe("calculateMedian", () => {
     { input: [1, 2, 3, 4], expected: 2.5 },
     { input: [1, 2, 3, 4, 5, 6], expected: 3.5 },
   ].forEach(({ input, expected }) =>
-    it(`returns the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   [
@@ -24,7 +25,8 @@ describe("calculateMedian", () => {
     { input: [110, 20, 0], expected: 20 },
     { input: [6, -2, 2, 12, 14], expected: 6 },
   ].forEach(({ input, expected }) =>
-    it(`returns the correct median for unsorted array [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`returns the correct median for unsorted array [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
   );
 
   it("doesn't modify the input array [3, 1, 2]", () => {
@@ -33,8 +35,17 @@ describe("calculateMedian", () => {
     expect(list).toEqual([3, 1, 2]);
   });
 
-  [ 'not an array', 123, null, undefined, {}, [], ["apple", null, undefined] ].forEach(val =>
-    it(`returns null for non-numeric array (${val})`, () => expect(calculateMedian(val)).toBe(null))
+  [
+    "not an array",
+    123,
+    null,
+    undefined,
+    {},
+    [],
+    ["apple", null, undefined],
+  ].forEach((val) =>
+    it(`returns null for non-numeric array (${val})`, () =>
+      expect(calculateMedian(val)).toBe(null))
   );
 
   [
@@ -45,6 +56,33 @@ describe("calculateMedian", () => {
     { input: [3, "apple", 1, null, 2, undefined, 4], expected: 2.5 },
     { input: ["banana", 5, 3, "apple", 1, 4, 2], expected: 3 },
   ].forEach(({ input, expected }) =>
-    it(`filters out non-numeric values and calculates the median for [${input}]`, () => expect(calculateMedian(input)).toEqual(expected))
+    it(`filters out non-numeric values and calculates the median for [${input}]`, () =>
+      expect(calculateMedian(input)).toEqual(expected))
+  );
+});
+
+describe("calculateMedian - ignores non-finite numbers", () => {
+  [
+    { input: [1, 2, NaN, 3], expected: 2 },
+    { input: [1, 2, Infinity, 3], expected: 2 },
+    { input: [1, 2, -Infinity, 3], expected: 2 },
+    { input: [1, 2, NaN, Infinity, -Infinity, 3], expected: 2 },
+    { input: [NaN, Infinity, -Infinity, 5, 10], expected: 7.5 },
+  ].forEach(({ input, expected }) =>
+    it(`ignores NaN/Infinity values in [${input}]`, () => {
+      expect(calculateMedian(input)).toEqual(expected);
+    })
   );
+
+  it("returns null when all values are non-finite", () => {
+    expect(calculateMedian([NaN, Infinity, -Infinity])).toBe(null);
+  });
+
+  it("handles mix of finite and non-finite with even count", () => {
+    expect(calculateMedian([1, 2, 3, 4, Infinity, NaN])).toBe(2.5);
+  });
+
+  it("handles mix of finite and non-finite with odd count", () => {
+    expect(calculateMedian([1, 2, 3, Infinity, NaN])).toBe(2);
+  });
 });

Sprint-1/implement/dedupe.js

@@ -1 +1,6 @@
-function dedupe() {}
+function dedupe(arr) {
+  if (arr.length === 0) return [];
+  return [...new Set(arr)];
+}
+
+module.exports = dedupe;

Sprint-1/implement/dedupe.test.js

@@ -1,27 +1,50 @@
-const dedupe = require("./dedupe.js");
-/*
-Dedupe Array
+const dedupe = require("./dedupe");
 
-📖 Dedupe means **deduplicate**
+describe("dedupe", () => {
+  // Given an empty array
+  // When passed to the dedupe function
+  // Then it should return an empty array
+  test.todo("given an empty array, it returns an empty array");
+  test("given an empty array, it returns an empty array", () => {
+    const result = dedupe([]);
+    expect(result).toEqual([]);
+  });
 
-In this kata, you will need to deduplicate the elements of an array
+  // Given an array with no duplicates
+  // When passed to the dedupe function
+  // Then it should return a copy of the original array
+  test("given an array with no duplicates, it returns a copy of the original array", () => {
+    const input = [1, 2, 3, 4];
+    const result = dedupe(input);
 
-E.g. dedupe(['a','a','a','b','b','c']) target output: ['a','b','c']
-E.g. dedupe([5, 1, 1, 2, 3, 2, 5, 8]) target output: [5, 1, 2, 3, 8]
-E.g. dedupe([1, 2, 1]) target output: [1, 2]
-*/
+    expect(result).toEqual([1, 2, 3, 4]);
+    expect(result).not.toBe(input); // should be a new copy
+  });
 
-// Acceptance Criteria:
+  // Given an array with strings
+  // When passed to the dedupe function
+  // Then it should remove duplicates preserving first occurrence
+  test("removes duplicate strings preserving first occurrence", () => {
+    const input = ["a", "a", "a", "b", "b", "c"];
+    const result = dedupe(input);
 
-// Given an empty array
-// When passed to the dedupe function
-// Then it should return an empty array
-test.todo("given an empty array, it returns an empty array");
+    expect(result).toEqual(["a", "b", "c"]);
+  });
 
-// Given an array with no duplicates
-// When passed to the dedupe function
-// Then it should return a copy of the original array
+  // Given an array with numbers
+  // When passed to the dedupe function
+  // Then it should remove the duplicate values, preserving the first occurence of each element
+  test("removes duplicate numbers preserving first occurrence", () => {
+    const input = [5, 1, 1, 2, 3, 2, 5, 8];
+    const result = dedupe(input);
 
-// Given an array with strings or numbers
-// When passed to the dedupe function
-// Then it should remove the duplicate values, preserving the first occurence of each element
+    expect(result).toEqual([5, 1, 2, 3, 8]);
+  });
+
+  test("removes duplicates in mixed order", () => {
+    const input = [1, 2, 1];
+    const result = dedupe(input);
+
+    expect(result).toEqual([1, 2]);
+  });
+});

Sprint-1/implement/max.js

@@ -1,4 +1,23 @@
 function findMax(elements) {
+  if (!Array.isArray(elements)) {
+    return -Infinity;
+  }
+
+  const numbers = elements.filter((el) => Number.isFinite(el));
+
+  if (numbers.length === 0) {
+    return -Infinity;
+  }
+
+  let max = numbers[0];
+
+  for (let i = 1; i < numbers.length; i++) {
+    if (numbers[i] > max) {
+      max = numbers[i];
+    }
+  }
+
+  return max;
 }
 
 module.exports = findMax;

Sprint-1/implement/max.test.js

@@ -1,43 +1,68 @@
-/* Find the maximum element of an array of numbers
-
-In this kata, you will need to implement a function that find the largest numerical element of an array.
+const findMax = require("./max.js");
 
-E.g. max([30, 50, 10, 40]), target output: 50
-E.g. max(['hey', 10, 'hi', 60, 10]), target output: 60 (sum ignores any non-numerical elements)
+describe("findMax", () => {
+  // Given an empty array
+  // When passed to the max function
+  // Then it should return -Infinity
+  test("given an empty array, returns -Infinity", () => {
+    expect(findMax([])).toBe(-Infinity);
+  });
 
-You should implement this function in max.js, and add tests for it in this file.
+  // Given an array with one number
+  // When passed to the max function
+  // Then it should return that number
+  test("given an array with one number, returns that number", () => {
+    expect(findMax([5])).toBe(5);
+  });
 
-We have set things up already so that this file can see your function from the other file.
-*/
+  // Given an array with both positive and negative numbers
+  // When passed to the max function
+  // Then it should return the largest number overall
+  test("returns the largest number from positive and negative numbers", () => {
+    expect(findMax([-10, 20, -5, 15])).toBe(20);
+  });
 
-const findMax = require("./max.js");
+  // Given an array with just negative numbers
+  // When passed to the max function
+  // Then it should return the closest one to zero
+  test("returns the largest number among negative numbers", () => {
+    expect(findMax([-10, -3, -50, -1])).toBe(-1);
+  });
 
-// Given an empty array
-// When passed to the max function
-// Then it should return -Infinity
-// Delete this test.todo and replace it with a test.
-test.todo("given an empty array, returns -Infinity");
+  // Given an array with decimal numbers
+  // When passed to the max function
+  // Then it should return the largest decimal number
+  test("returns the largest decimal number", () => {
+    expect(findMax([1.2, 3.7, 2.5, 3.6])).toBe(3.7);
+  });
 
-// Given an array with one number
-// When passed to the max function
-// Then it should return that number
+  // Given an array with non-number values
+  // When passed to the max function
+  // Then it should return the max and ignore non-numeric values
+  test("ignores non-number values (including numeric strings)", () => {
+    expect(findMax(["hey", 10, "300", 60, 10])).toBe(60);
+  });
 
-// Given an array with both positive and negative numbers
-// When passed to the max function
-// Then it should return the largest number overall
+  // Given an array with only non-number values
+  // When passed to the max function
+  // Then it should return the least surprising value given how it behaves for all other inputs
+  test("returns -Infinity when array has only non-number values", () => {
+    expect(findMax(["a", "b", "c"])).toBe(-Infinity);
+  });
 
-// Given an array with just negative numbers
-// When passed to the max function
-// Then it should return the closest one to zero
+  test("does not treat numeric strings as numbers", () => {
+    expect(findMax([20, "300"])).toBe(20);
+  });
 
-// Given an array with decimal numbers
-// When passed to the max function
-// Then it should return the largest decimal number
+  test("returns -Infinity when only numeric strings are present", () => {
+    expect(findMax(["100", "200", "300"])).toBe(-Infinity);
+  });
 
-// Given an array with non-number values
-// When passed to the max function
-// Then it should return the max and ignore non-numeric values
+  test("ignores NaN and Infinity values", () => {
+    expect(findMax([10, NaN, 50, Infinity, -Infinity])).toBe(50);
+  });
 
-// Given an array with only non-number values
-// When passed to the max function
-// Then it should return the least surprising value given how it behaves for all other inputs
+  test("returns -Infinity when only NaN and Infinity are present", () => {
+    expect(findMax([NaN, Infinity, -Infinity])).toBe(-Infinity);
+  });
+});

Sprint-1/implement/sum.js

@@ -1,4 +1,7 @@
 function sum(elements) {
+  const numbers = elements.filter((el) => Number.isFinite(el));
+  const sumNumbers = numbers.reduce((a, b) => a + b, 0);
+  return sumNumbers;
 }
 
 module.exports = sum;