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| 1 | +/** |
| 2 | + * Data-Structures-In-Java |
| 3 | + * CollectionUtils.java |
| 4 | + */ |
| 5 | +package com.deepak.data.structures.Utils; |
| 6 | + |
| 7 | +import java.util.ArrayList; |
| 8 | +import java.util.Comparator; |
| 9 | +import java.util.List; |
| 10 | +import java.util.Random; |
| 11 | + |
| 12 | +/** |
| 13 | + * Utilities for collections i.e List |
| 14 | + * |
| 15 | + * @author Deepak |
| 16 | + */ |
| 17 | +public class CollectionUtils { |
| 18 | + |
| 19 | + /** |
| 20 | + * Method to check if list is empty |
| 21 | + * |
| 22 | + * @param list |
| 23 | + * @return {@link boolean} |
| 24 | + */ |
| 25 | + public static <T> boolean isEmpty(List<T> list) { |
| 26 | + return list == null || list.size() == 0; |
| 27 | + } |
| 28 | + |
| 29 | + /** |
| 30 | + * Method to sort the list with no comparator |
| 31 | + * |
| 32 | + * @param list |
| 33 | + * @return {@link List<T>} |
| 34 | + */ |
| 35 | + public static <T> List<T> sort(List<T> list) { |
| 36 | + list.sort(null); |
| 37 | + return list; |
| 38 | + } |
| 39 | + |
| 40 | + /** |
| 41 | + * Method to sort the list with custom comparator |
| 42 | + * |
| 43 | + * @param list |
| 44 | + * @param comparator |
| 45 | + * @return {@link List<T>} |
| 46 | + */ |
| 47 | + public static <T> List<T> sort(List<T> list, Comparator<T> comparator) { |
| 48 | + list.sort(comparator); |
| 49 | + return list; |
| 50 | + } |
| 51 | + |
| 52 | + /** |
| 53 | + * Method to perform a binary search |
| 54 | + * |
| 55 | + * @param list |
| 56 | + * @param element |
| 57 | + * @param comparator |
| 58 | + * @return {@link T} |
| 59 | + */ |
| 60 | + public static <T> T binarySearch(List<T> list, T element, Comparator<T> comparator) { |
| 61 | + if (list.isEmpty()) { |
| 62 | + return null; |
| 63 | + } |
| 64 | + int low = 0; |
| 65 | + int high = list.size() - 1; |
| 66 | + while (high > low) { |
| 67 | + int mid = (low + high) / 2; |
| 68 | + if (list.get(mid) == element) { |
| 69 | + return element; |
| 70 | + } else if (comparator.compare(list.get(mid), element) > 0) { |
| 71 | + high = mid - 1; |
| 72 | + } else { |
| 73 | + low = mid + 1; |
| 74 | + } |
| 75 | + } |
| 76 | + return null; |
| 77 | + } |
| 78 | + |
| 79 | + /** |
| 80 | + * Method to reverse the list |
| 81 | + * |
| 82 | + * @param list |
| 83 | + * @return {@link List<T>} |
| 84 | + */ |
| 85 | + public static <T> List<T> reverse(List<T> list) { |
| 86 | + if (list != null && list.size() > 0) { |
| 87 | + List<T> updatedList = new ArrayList<>(); |
| 88 | + for (int i = list.size() - 1; i >= 0; i--) { |
| 89 | + updatedList.add(list.get(i)); |
| 90 | + } |
| 91 | + return updatedList; |
| 92 | + } |
| 93 | + return null; |
| 94 | + } |
| 95 | + |
| 96 | + /** |
| 97 | + * Method to shuffle the list |
| 98 | + * |
| 99 | + * @param list |
| 100 | + * @return {@link List<T>} |
| 101 | + */ |
| 102 | + public static <T> List<T> shuffle(List<T> list) { |
| 103 | + if (list != null && list.size() > 0) { |
| 104 | + List<T> updatedList = new ArrayList<>(); |
| 105 | + final int[] ints = new Random().ints(0, list.size()).distinct().limit(list.size()).toArray(); |
| 106 | + for (int i = 0; i < ints.length; i++) { |
| 107 | + updatedList.add(list.get(i)); |
| 108 | + } |
| 109 | + return updatedList; |
| 110 | + } |
| 111 | + return null; |
| 112 | + } |
| 113 | + |
| 114 | + /** |
| 115 | + * Method to swap elements at two indexes |
| 116 | + * |
| 117 | + * @param list |
| 118 | + * @param minIndex |
| 119 | + * @param maxIndex |
| 120 | + * @return {@link List<T>} |
| 121 | + */ |
| 122 | + public static <T> List<T> swap(List<T> list, int minIndex, int maxIndex) { |
| 123 | + if (list != null && list.size() > 2 && maxIndex > minIndex) { |
| 124 | + T elementAtMinIndex = list.get(minIndex); |
| 125 | + T elementAtMaxIndex = list.get(maxIndex); |
| 126 | + list.add(minIndex, elementAtMaxIndex); |
| 127 | + list.add(maxIndex, elementAtMinIndex); |
| 128 | + return list; |
| 129 | + } |
| 130 | + return null; |
| 131 | + } |
| 132 | + |
| 133 | + /** |
| 134 | + * Method to fill the list with the given element |
| 135 | + * |
| 136 | + * @param list |
| 137 | + * @param element |
| 138 | + * @return {@link List<T>} |
| 139 | + */ |
| 140 | + public static <T> List<T> fill(List<T> list, T element) { |
| 141 | + if (list != null && list.size() > 0) { |
| 142 | + for (int i = 0; i < list.size(); i++) { |
| 143 | + list.add(i, element); |
| 144 | + } |
| 145 | + return list; |
| 146 | + } |
| 147 | + return null; |
| 148 | + } |
| 149 | + |
| 150 | + /** |
| 151 | + * Method to find the minimum from the list |
| 152 | + * |
| 153 | + * @param list |
| 154 | + * @param comparator |
| 155 | + * @return {@link T} |
| 156 | + */ |
| 157 | + public static <T> T min(List<T> list, Comparator<T> comparator) { |
| 158 | + return null; |
| 159 | + } |
| 160 | + |
| 161 | + public static <T> T max(List<T> list, Comparator<T> comparator) { |
| 162 | + return null; |
| 163 | + } |
| 164 | + |
| 165 | + public static <T> List<T> rotate(List<T> list, int n) { |
| 166 | + return null; |
| 167 | + } |
| 168 | + |
| 169 | +} |
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