day02--课后练习

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编程题
1：计算付款金额: 一杯5元, 每两杯的第二杯半价(杯数由用户从键盘录入 ) 如: 5杯 = (5+2.5)*2 + 5 = 20

package homework;import java.util.Scanner;public class homework01 {    public static void main(String[] args) {        System.out.println("饮料一杯5元，每两杯的第二杯半价");        System.out.println("请输入您需要购买的饮料杯数");        Scanner scanner = new Scanner(System.in);        int a = scanner.nextInt();        int count = a % 2;        double sum = 0;        String result = "";        scanner.close();        if (count == 0) {            sum = (5 + 2.5) * (a / 2);            result = "(5+2.5)*" + a / 2 + "=" + sum;        }        else {            sum = (5 + 2.5) * (a / 2) + 5;            result = "(5+2.5)*" + a / 2 + "+5=" + sum;        }        System.out.println(result);        System.out.println(sum);    }}

2:分别统计字符串”123456789012”奇数位及偶数位上的数字的和
将字符串的奇数位数字相加求和 c1 = 1 + 3 + 5 + 7 + 9 + 1
将字符串的偶数位数字相加求和 c2 = 2 + 4 + 6 + 8 + 0 + 2

package homework;import java.util.Scanner;public class homework02 {    public static void main(String[] args) {        System.out.println("本程序功能:统计字符串数字奇数位及偶数为上的数字的和");        System.out.println("请输入您需要统计的字符串数字");        Scanner scanner = new Scanner(System.in);        String s = scanner.next();        scanner.close();        int sum1 = 0, sum2 = 0;        String result1 = "", result2 = "";        char[] cs = s.toCharArray();        for (int i = 0; i < cs.length; i++) {            if (i % 2 == 0) {                sum1 += Integer.parseInt(cs[i] + "");                if (i == cs.length - 1) {                    result1 = cs[i] + " " + result1;                } else {                    result1 = cs[i] + "+" + result1;                }            } else {                sum2 += Integer.parseInt(cs[i] + "");                result2 = cs[i] + "+" + result2;            }        }        System.out.println(result1 + " =" + sum1);        System.out.println(result2 + " =" + sum2);    }}

3：String[] cards = {“3”,”4”,”8”,”A”,”K”,”Q”}数组中存储了6张牌，设计一个算法把牌打乱，也就是实现洗牌功能

package homework;import java.util.Random;public class homework03 {    public static void check(int[] nums, int num) {        int i;        Random random = new Random();        for (i = 0; i < num; i++) {            if (nums[i] == nums[num]) {                nums[num] = random.nextInt(6);                check(nums, num);            }        }        if (i == num)            return;    }    public static void main(String[] args) {        System.out.println("本程序功能,实现洗牌功能");        String[] cards = { "3", "4", "8", "A", "K", "Q" };        Random random = new Random();        int[] copyCards = new int[cards.length];        for (int i = 0; i < cards.length; i++) {            copyCards[i] = random.nextInt(6);            check(copyCards, i);            System.out.print(cards[copyCards[i]]+" ");        }    }}

4：一个5位的整数，判断它是不是回文数，例如12321是回文数

5：向一个有序的整型数组中插入一个数，插入后该数组还是有序的
(使用二分法)()

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