| 4 | 4 | // |
| 5 | 5 | |
| 6 | 6 | export class List { |
| 7 | | constructor() { |
| 8 | | throw new Error('Remove this line and implement the function'); |
| 7 | /** |
| 8 | * Creates a new List instance. |
| 9 | * @param {Array} [values=[]] - Initial values for the list. |
| 10 | */ |
| 11 | constructor(values = []) { |
| 12 | this.values = values; |
| 9 | 13 | } |
| 10 | 14 | |
| 11 | 15 | /** |
| 12 | | * @param {List} other |
| 13 | | * @return {List} |
| 16 | * Appends all items from another list to the end of this list. |
| 17 | * @param {List} other - The list to append. |
| 18 | * @return {List} A new list containing all items from both lists. |
| 19 | * |
| 20 | * Handled Edge Cases: |
| 21 | * - When other list is empty |
| 22 | * - When this list is empty |
| 14 | 23 | */ |
| 15 | 24 | append(other) { |
| 16 | | throw new Error('Remove this line and implement the function'); |
| 25 | // Edge Case: When other list is empty, return a copy of this list |
| 26 | if (!other || other.length() === 0) { |
| 27 | return new List(this.values); |
| 28 | } |
| 29 | |
| 30 | // Edge Case: When this list is empty, return a copy of the other list |
| 31 | if (this.length() === 0) { |
| 32 | return new List(other.values); |
| 33 | } |
| 34 | |
| 35 | return new List(this.values.concat(other.values)); |
| 17 | 36 | } |
| 18 | 37 | |
| 19 | 38 | /** |
| 20 | | * @param {List} others |
| 21 | | * @return {List} |
| 39 | * Concatenates a series of lists into one flattened list. |
| 40 | * @param {List} others - A list containing other lists to concatenate. |
| 41 | * @return {List} A new list with all items from all lists. |
| 42 | * |
| 43 | * Handled Edge Cases: |
| 44 | * - When others list is empty |
| 45 | * - When this list is empty |
| 46 | * - When nested lists are empty |
| 22 | 47 | */ |
| 23 | 48 | concat(others) { |
| 24 | | throw new Error('Remove this line and implement the function'); |
| 49 | // Edge Case: When others list is empty, return a copy of this list |
| 50 | if (!others || others.length() === 0) { |
| 51 | return new List(this.values); |
| 52 | } |
| 53 | |
| 54 | let result = new List(this.values); |
| 55 | |
| 56 | // Process each list in the others list |
| 57 | for (let i = 0; i < others.length(); i++) { |
| 58 | const item = others.values[i]; |
| 59 | |
| 60 | // Edge Case: Handle nested List objects |
| 61 | if (item instanceof List) { |
| 62 | result = result.append(item); |
| 63 | } else { |
| 64 | // Edge Case: Handle non-List items (should not normally occur based on problem description) |
| 65 | result = result.append(new List([item])); |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | return result; |
| 25 | 70 | } |
| 26 | 71 | |
| 27 | 72 | /** |
| 28 | | * @param {(any) => boolean} predicate |
| 29 | | * @return {List} |
| 73 | * Filters the list based on a predicate function. |
| 74 | * @param {Function} predicate - Function that returns true for items to keep. |
| 75 | * @return {List} A new list containing only items for which predicate returned true. |
| 76 | * |
| 77 | * Handled Edge Cases: |
| 78 | * - When this list is empty |
| 79 | * - When no items match the predicate |
| 80 | * - When all items match the predicate |
| 30 | 81 | */ |
| 31 | 82 | filter(predicate) { |
| 32 | | throw new Error('Remove this line and implement the function'); |
| 83 | // Edge Case: When this list is empty, return an empty list |
| 84 | if (this.length() === 0) { |
| 85 | return new List([]); |
| 86 | } |
| 87 | |
| 88 | const filtered = []; |
| 89 | |
| 90 | for (let i = 0; i < this.values.length; i++) { |
| 91 | if (predicate(this.values[i])) { |
| 92 | filtered.push(this.values[i]); |
| 93 | } |
| 94 | } |
| 95 | |
| 96 | // Edge Case: When no items match (filtered array is empty) |
| 97 | // Edge Case: When all items match (filtered array equals original) |
| 98 | return new List(filtered); |
| 33 | 99 | } |
| 34 | 100 | |
| 35 | 101 | /** |
| 36 | | * @param {(any) => any} expression |
| 37 | | * @return {List} |
| 102 | * Maps a function over each item in the list. |
| 103 | * @param {Function} expression - Function to apply to each item. |
| 104 | * @return {List} A new list containing the results of applying the function. |
| 105 | * |
| 106 | * Handled Edge Cases: |
| 107 | * - When this list is empty |
| 38 | 108 | */ |
| 39 | 109 | map(expression) { |
| 40 | | throw new Error('Remove this line and implement the function'); |
| 110 | // Edge Case: When this list is empty, return an empty list |
| 111 | if (this.length() === 0) { |
| 112 | return new List([]); |
| 113 | } |
| 114 | |
| 115 | const mapped = []; |
| 116 | |
| 117 | for (let i = 0; i < this.values.length; i++) { |
| 118 | mapped.push(expression(this.values[i])); |
| 119 | } |
| 120 | |
| 121 | return new List(mapped); |
| 41 | 122 | } |
| 42 | 123 | |
| 43 | 124 | /** |
| 44 | | * @return {number} |
| 125 | * Returns the number of items in the list. |
| 126 | * @return {number} The count of items. |
| 127 | * |
| 128 | * Handled Edge Cases: |
| 129 | * - When list is empty (returns 0) |
| 45 | 130 | */ |
| 46 | 131 | length() { |
| 47 | | throw new Error('Remove this line and implement the function'); |
| 132 | // Edge Case: When list is empty, return 0 |
| 133 | let count = 0; |
| 134 | for (let i = 0; i < this.values.length; i++) { |
| 135 | count++; |
| 136 | } |
| 137 | return count; |
| 48 | 138 | } |
| 49 | 139 | |
| 50 | 140 | /** |
| 51 | | * @param {(acc: any, el: any) => any} callback |
| 52 | | * @param {any} initial |
| 53 | | * @return {any} |
| 141 | * Folds (reduces) the list from the left using a callback function. |
| 142 | * @param {Function} callback - Function to apply to accumulator and each element. |
| 143 | * @param {any} initial - Initial value for the accumulator. |
| 144 | * @return {any} The final accumulator value. |
| 145 | * |
| 146 | * Handled Edge Cases: |
| 147 | * - When this list is empty (returns initial value) |
| 54 | 148 | */ |
| 55 | 149 | foldl(callback, initial) { |
| 56 | | throw new Error('Remove this line and implement the function'); |
| 150 | // Edge Case: When this list is empty, return the initial value |
| 151 | if (this.length() === 0) { |
| 152 | return initial; |
| 153 | } |
| 154 | |
| 155 | let accumulator = initial; |
| 156 | |
| 157 | for (let i = 0; i < this.values.length; i++) { |
| 158 | accumulator = callback(accumulator, this.values[i]); |
| 159 | } |
| 160 | |
| 161 | return accumulator; |
| 57 | 162 | } |
| 58 | 163 | |
| 59 | 164 | /** |
| 60 | | * @param {(acc: any, el: any) => any} callback |
| 61 | | * @param {any} initial |
| 62 | | * @return {any} |
| 165 | * Folds (reduces) the list from the right using a callback function. |
| 166 | * @param {Function} callback - Function to apply to accumulator and each element. |
| 167 | * @param {any} initial - Initial value for the accumulator. |
| 168 | * @return {any} The final accumulator value. |
| 169 | * |
| 170 | * Handled Edge Cases: |
| 171 | * - When this list is empty (returns initial value) |
| 63 | 172 | */ |
| 64 | 173 | foldr(callback, initial) { |
| 65 | | throw new Error('Remove this line and implement the function'); |
| 174 | // Edge Case: When this list is empty, return the initial value |
| 175 | if (this.length() === 0) { |
| 176 | return initial; |
| 177 | } |
| 178 | |
| 179 | let accumulator = initial; |
| 180 | |
| 181 | // Process from right to left |
| 182 | for (let i = this.values.length - 1; i >= 0; i--) { |
| 183 | accumulator = callback(accumulator, this.values[i]); |
| 184 | } |
| 185 | |
| 186 | return accumulator; |
| 66 | 187 | } |
| 67 | 188 | |
| 68 | 189 | /** |
| 69 | | * @return {List} |
| 190 | * Reverses the order of items in the list. |
| 191 | * @return {List} A new list with items in reversed order. |
| 192 | * |
| 193 | * Handled Edge Cases: |
| 194 | * - When this list is empty |
| 195 | * - When this list has only one element |
| 70 | 196 | */ |
| 71 | 197 | reverse() { |
| 72 | | throw new Error('Remove this line and implement the function'); |
| 198 | // Edge Case: When this list is empty, return an empty list |
| 199 | if (this.length() === 0) { |
| 200 | return new List([]); |
| 201 | } |
| 202 | |
| 203 | // Edge Case: When this list has only one element, return a copy of the list |
| 204 | if (this.length() === 1) { |
| 205 | return new List([this.values[0]]); |
| 206 | } |
| 207 | |
| 208 | const reversed = []; |
| 209 | |
| 210 | for (let i = this.values.length - 1; i >= 0; i--) { |
| 211 | reversed.push(this.values[i]); |
| 212 | } |
| 213 | |
| 214 | return new List(reversed); |
| 73 | 215 | } |
| 74 | 216 | } |