mirror of
https://github.com/krahets/hello-algo.git
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e720aa2d24
* Sync recent changes to the revised Word. * Revised the preface chapter * Revised the introduction chapter * Revised the computation complexity chapter * Revised the chapter data structure * Revised the chapter array and linked list * Revised the chapter stack and queue * Revised the chapter hashing * Revised the chapter tree * Revised the chapter heap * Revised the chapter graph * Revised the chapter searching * Reivised the sorting chapter * Revised the divide and conquer chapter * Revised the chapter backtacking * Revised the DP chapter * Revised the greedy chapter * Revised the appendix chapter * Revised the preface chapter doubly * Revised the figures
105 lines
2.6 KiB
Dart
105 lines
2.6 KiB
Dart
/**
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* File: array.dart
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* Created Time: 2023-01-20
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* Author: Jefferson (JeffersonHuang77@gmail.com)
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*/
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// ignore_for_file: unused_local_variable
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import 'dart:math';
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/* 随机访问元素 */
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int randomAccess(List<int> nums) {
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// 在区间 [0, nums.length) 中随机抽取一个数字
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int randomIndex = Random().nextInt(nums.length);
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// 获取并返回随机元素
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int randomNum = nums[randomIndex];
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return randomNum;
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}
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/* 扩展数组长度 */
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List<int> extend(List<int> nums, int enlarge) {
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// 初始化一个扩展长度后的数组
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List<int> res = List.filled(nums.length + enlarge, 0);
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// 将原数组中的所有元素复制到新数组
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for (var i = 0; i < nums.length; i++) {
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res[i] = nums[i];
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}
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// 返回扩展后的新数组
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return res;
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}
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/* 在数组的索引 index 处插入元素 _num */
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void insert(List<int> nums, int _num, int index) {
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// 把索引 index 以及之后的所有元素向后移动一位
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for (var i = nums.length - 1; i > index; i--) {
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nums[i] = nums[i - 1];
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}
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// 将 _num 赋给 index 处元素
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nums[index] = _num;
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}
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/* 删除索引 index 处的元素 */
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void remove(List<int> nums, int index) {
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// 把索引 index 之后的所有元素向前移动一位
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for (var i = index; i < nums.length - 1; i++) {
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nums[i] = nums[i + 1];
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}
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}
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/* 遍历数组元素 */
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void traverse(List<int> nums) {
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int count = 0;
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// 通过索引遍历数组
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for (var i = 0; i < nums.length; i++) {
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count += nums[i];
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}
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// 直接遍历数组元素
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for (int _num in nums) {
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count += _num;
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}
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// 通过 forEach 方法遍历数组
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nums.forEach((_num) {
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count += _num;
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});
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}
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/* 在数组中查找指定元素 */
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int find(List<int> nums, int target) {
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for (var i = 0; i < nums.length; i++) {
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if (nums[i] == target) return i;
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}
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return -1;
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}
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/* Driver Code */
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void main() {
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/* 初始化数组 */
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var arr = List.filled(5, 0);
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print('数组 arr = $arr');
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List<int> nums = [1, 3, 2, 5, 4];
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print('数组 nums = $nums');
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/* 随机访问 */
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int randomNum = randomAccess(nums);
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print('在 nums 中获取随机元素 $randomNum');
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/* 长度扩展 */
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nums = extend(nums, 3);
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print('将数组长度扩展至 8 ，得到 nums = $nums');
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/* 插入元素 */
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insert(nums, 6, 3);
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print("在索引 3 处插入数字 6 ，得到 nums = $nums");
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/* 删除元素 */
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remove(nums, 2);
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print("删除索引 2 处的元素，得到 nums = $nums");
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/* 遍历数组 */
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traverse(nums);
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/* 查找元素 */
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int index = find(nums, 3);
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print("在 nums 中查找元素 3 ，得到索引 = $index");
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}
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