20240407蓝桥杯备赛
- 1、学习蓝桥云课省赛冲刺课 【3-搜索算法】【4-枚举与尺度法】
- 2、学习蓝桥云课Java省赛无忧班 【1-语言基础】
- 3、代码练习
- 数字反转
- 数字反转优化算法
- sort排序相关
- String字符串相关
- StringBuilder字符串相关
- HashSet相关
1、学习蓝桥云课省赛冲刺课 【3-搜索算法】【4-枚举与尺度法】
2、学习蓝桥云课Java省赛无忧班 【1-语言基础】
3、代码练习
数字反转
package THL_0407;import java.util.Scanner;public class Demo01 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int num = sc.nextInt(); if (num > 0) { StringBuilder string = new StringBuilder(); string.append(num); StringBuilder string1 = new StringBuilder();string1 = string.reverse(); String string2 = string1.toString(); int num1 = Integer.valueOf(string2); System.out.println(num1); } else { num = num * (-1); StringBuilder string = new StringBuilder(); string.append(num); StringBuilder string1 = new StringBuilder();string1 = string.reverse(); String string2 = string1.toString(); int num1 = Integer.valueOf(string2); num1 = num1 * (-1); System.out.println(num1); }}
}
数字反转优化算法
package THL_0407;import java.util.Scanner;
import java.lang.Math;public class Demo02 {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int num = sc.nextInt(); StringBuilder string = new StringBuilder(); string.append(Math.abs(num)); StringBuilder reversedString = string.reverse(); int reversedNum = Integer.parseInt(reversedString.toString()); if (num < 0) { reversedNum *= -1; }System.out.println(reversedNum); }
}
sort排序相关
package THL_0407;import java.util.Arrays;
import java.util.*;
import java.util.List;import com.sun.jdi.connect.spi.Connection;public class Demo_sort {public static void main(String[] args) {List<Integer> list = new ArrayList<>();list.add(8);list.add(4);list.add(5);list.add(6);list.add(9);list.add(3);list.add(1);Collections.sort(list);for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();Collections.sort(list,new Comparator<Integer>() {@Overridepublic int compare(Integer o1, Integer o2) {return o2-o1;}});for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();Collections.sort(list,(o1,o2)->o2-o1); System.out.print("实现降序排序:");for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();Collections.sort(list,(o1,o2)->o1-o2); System.out.print("实现升序排序:");for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();
}}
String字符串相关
package THL_0407;import java.util.Scanner;public class Demo_String {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String string0 = "hahaha"; String string = sc.nextLine(); System.out.println("string = " + string); System.out.println("string的第三个字符为 = " + string.charAt(2)); System.out.println("string0和string1作比较:" + (string0.compareTo(string) == 0 ? "相同" : "不同")); String string1 = "fighting"; System.out.println("连接字符串string0+string1 = " + string0.concat(string1)); String string2 = "hahahafighting"; System.out.println("string2与连接的字符串作比较:" + string2.equals(string0.concat(string1))); String string3 = "helloworldhello"; System.out.println("world在字符串string3中第一次出现的索引下标为:" + string3.indexOf("world")); System.out.println("hahah在字符串string3中第一次出现的索引下标为:" + string3.indexOf("hahaha")); String string4 = "hello world zoe haha"; System.out.println("string4的索引区间[12,15):" + string4.substring(12, 15)); String string5 = "helloworld"; char[] ch = string5.toCharArray(); for (int i = 0; i < ch.length; i++) { System.out.print(ch[i]); }System.out.println();String string6 = ""; System.out.println("string5是否是空字符串:" + string5.isEmpty()); System.out.println("string6是否是空字符串:" + string6.isEmpty());String str = sc.nextLine(); String str1 = sc.next(); System.out.println(str); System.out.println(str1); String[] str2 = str.split(" "); System.out.println("str2.length = " + str2.length); for (int i = 0; i < str2.length; i++) { System.out.print(str2[i] + " "); }System.out.println();String[] str3 = str.split(" ", 3); System.out.println("str3.length = " + str3.length); for (int i = 0; i < str3.length; i++) { System.out.print(str3[i] + " "); }System.out.println();sc.close(); }
}
StringBuilder字符串相关
package THL_0407;import java.util.Scanner;public class Demo_StringBuilder {public static void main(String[] args) {Scanner sc = new Scanner(System.in);String string = sc.nextLine(); StringBuilder str = new StringBuilder(); str.append(string); StringBuilder str1 = new StringBuilder();str1 = str.reverse(); System.out.println("string = " + string); System.out.println("string反转后为 = " + str1); int num = 265512000; String string1 = num + ""; StringBuilder str2 = new StringBuilder();str2.append(string1); str2 = str2.reverse(); String string2 = str2.toString(); int num1 = Integer.valueOf(string2); System.out.println("num反转输出为:" + num1); StringBuilder string3 = new StringBuilder();string3.append("zoe,helloworld"); System.out.println("hello字符串第一次出现的位置为:" + string3.indexOf("hello")); StringBuilder string4 = new StringBuilder();string4.append(""); System.out.println("string3是空字符串吗?" + string3.isEmpty()); System.out.println("string4是空字符串吗?" + string4.isEmpty());System.out.println("string3索引为3的字符为:" + string3.charAt(3)); sc.close(); }
}
HashSet相关
package THL_0407;import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;public class Demo_set {public static void main(String[] args) {Set<Integer> set = new HashSet<>();set.add(8);set.add(2);set.add(8);set.add(2);set.add(7);set.add(2);set.add(5);set.add(2);for (Integer integer : set) {System.out.print(integer+" ");}System.out.println();ArrayList<Integer> list = new ArrayList<>(set);Collections.sort(list);System.out.print("升序输出:");for (Integer integer : list) {System.out.print(integer+" ");}System.out.println();Collections.sort(list,(o1,o2)->o2-o1);System.out.print("降序输出:");for (Integer integer : list) {System.out.print(integer+" ");}System.out.println(); }}
package THL_0407;import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;public class Demo_set02 {public static void main(String[] args) {Set<String> set1 = new HashSet<>();set1.add("h");set1.add("e");set1.add("l");set1.add("l");set1.add("o");Scanner sc = new Scanner(System.in);String str = sc.nextLine();Set<String> set = new HashSet<>();for (int i = 0; i < str.length(); i++) {set.add(String.valueOf(str.charAt(i)));}int count = 0;for (String string : set) {if(set1.contains(string)) {count++;}}System.out.println(count);set1.remove("l");System.out.println(set.contains("l"));set.retainAll(set1);System.out.println(set.size());set.clear();System.out.println(set.size());}
}