Java编程基础阶段笔记 day05 数组
发表于：2024-11-28 作者：热门IT资讯网编辑
编辑最后更新 2024年11月28日，数组笔记Notes数组介绍数组的声明数组初始化数组元素默认值数组复制数组反转数组查找：线性查找、二分查找数组排序：冒泡排序数组介绍数组名： 创建数组内存中开辟一整块连续的空间，而数组名中引用的是这块连
数组 |
笔记Notes
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int[] age = { 1, 2, 3, 4, 5, 6 };
/* * 数组中常见的算法 * 1. 求数组中元素的最大值、最小值、平均值、总和等 * 2. 数组的复制、反转、查找（线性查找、二分查找（了解）） * 3. 数组元素的排序算法:冒泡排序 */public class ArrayAlgorithm { public static void main(String[] args) { // 数组最大值、最小值、平均值、总和 System.out.println("---------------------------------数组最大值、最小值、平均值、总和--------------------------"); int scores[] = new int[5]; for (int i = 0; i < scores.length; i++) { scores[i] = (int) (Math.random() * 10); } for (int i = 0; i < scores.length; i++) { System.out.print(scores[i] + " "); } System.out.println(); int max = scores[0]; int min = scores[0]; int add = scores[0]; double ever = 0; for (int i = 0; i < scores.length; i++) { if (max < scores[i]) { max = scores[i]; } if (min > scores[i]) { min = scores[i]; } add += scores[i]; } ever = add / scores.length; System.out.println("max = " + max + " min = " + min + " add = " + add + " ever = " + ever); System.out.println("-------------------------------------------------------------"); System.out.println("----------------------------数组复制---------------------------------------------"); int copyScores[] = new int[scores.length]; for (int i = 0; i < copyScores.length; i++) { copyScores[i] = scores[i]; } for (int i = 0; i < copyScores.length; i++) { System.out.print(copyScores[i] + " "); } System.out.println(); System.out.println("---------------------------数组反转方法一---------------------------------------"); // 方法一 System.out.println("方法一"); int reverse[] = new int[scores.length]; for (int i = 0, j = scores.length - 1; i < scores.length && j >= 0; i++, j--) { reverse[i] = scores[j]; } for (int i = 0; i < reverse.length; i++) { System.out.print(reverse[i] + " "); } System.out.println(); System.out.println("--------------------------"); for (int i = 0; i < scores.length; i++) { System.out.print(scores[i] + " "); } System.out.println(); System.out.println("----------------------------数组反转方法二-----------------------------------"); for (int i = 0; i < scores.length / 2; i++) { int temp = scores[i]; scores[i] = scores[scores.length - i - 1]; scores[scores.length - i - 1] = temp; } for (int i = 0; i < scores.length; i++) { System.out.print(scores[i] + " "); } System.out.println(); System.out.println("-------------------------数组查找-线性查找-------------------------"); int[] numbers = { 1, 10, 9, 8, 20 }; // 线性查找 int findNumber = 18; // 要查找数值 int index = -1;//查找到的数值所对应的下标 for (int i = 0; i < numbers.length; i++) { if (findNumber ==numbers[i]) { index = i; break;//只查找一个 } } if (index != -1) { System.out.println("查找到数值！所对应的数组下标为：" + index); } else { System.out.println("查找不到值！"); } System.out.println("------------------------数组查找- 二分查找--------------------------------"); int[] number2 = { 12, 30, -5, 6, 9, 10, 5 }; //排序 Arrays.sort(number2); // 必须排序好 for (int i = 0; i < number2.length; i++) { System.out.print(number2[i] + " "); } System.out.println(); int findNumber2 = 12;//要查找的内容 int start = 0; int end = number2.length-1; int index2 = -1; //所在元素位置 while (start <= end) { int mid = (start + end) / 2; if (number2[mid] == findNumber2) { index2 = mid; break; } if(number2[mid] > findNumber2){ end = mid - 1; }else { start = mid + 1; } } if (index2 != -1) { System.out.println("你要的商品存在，在位置：" + index2); }else { System.out.println("客官您的包裹丟了"); } System.out.println("------------------------------冒泡排序（必须会手写）-------------------------------------"); int[] numbers3 = {10,2,89,39,16}; for (int i = 0; i < numbers3.length; i++) { System.out.print(numbers3[i] + " "); } System.out.println(); System.out.println("------------------------------排序前--------------------------------------------------------"); for (int i = 0; i < numbers3.length -1; i++) { //外排序次数为长度-1 为5-1 = 4 for (int j = 0; j < numbers3.length -1 - i; j++) { //内排序次数每次递减 4 3 2 1 if (numbers3[j] > numbers3[j+1]) { int temp = numbers3[j]; numbers3[j] = numbers3[j+1]; numbers3[j+1] = temp; } } } System.out.println("--------------------------排序后-------------------------------------------"); for (int i = 0; i < numbers3.length; i++) { System.out.print(numbers3[i] + " "); } System.out.println(); System.out.println("------------------------排序完成------------------------------------"); }} |
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