Contest1620 – 2020-2021-2学期《Java Web 系统开发》:java基础：字符串

废江_小江

发布于 2022-09-05 13:41:12

2980

发布于 2022-09-05 13:41:12

文章被收录于专栏：总栏目

QuestionA

import java.util.*;
public class Main {
	public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        String str = cin.next();
        String str2 ="";
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)>=65&&str.charAt(i)<=90||str.charAt(i)>=97&&str.charAt(i)<=122)
                str2=str2+str.charAt(i);
        }
        System.out.println(str2);
        //TODO
        cin.close();
    }
}

对输入的字符串进行遍历，charAt访问string字符串字符，大写英文字母字符65-90；小写英文字符97-122，要记住。java字符串可以直接拼接，并且string拼接后的字符串其实是jvm中新的一个字符串，这也是为什么使用太多字符串常量消耗空间，这里说多了。直接判断后进行拼接即可，输出str2。

QuestionB

import java.util.*;
public class Main {
	static String check(String str){
        //去掉字符串中多余的符号，只留下字母
        String str2 ="";
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)>=65&&str.charAt(i)<=90||str.charAt(i)>=97&&str.charAt(i)<=122)
                str2=str2+str.charAt(i);
        }
        return str2;
    }
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        String str = cin.next();
        String str2 = check(str);
        System.out.println(str2.length());
        cin.close();
    }
}

这里，写了一个去掉非字母的字符串函数，调用函数去掉输入的字符串的非字母后，直接输出字符串的长度即可。

QuestionC

import java.util.*;
public class Main {
public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        int n = cin.nextInt();
        int i=0;
        int sum=0;
        for(i=1;;i++){
            sum=i*i*i+sum;
            if(sum>n)
                break;
        }
        System.out.println(i-1);
        cin.close();
    }
}

暴力循环求解即可，没什么好说的

QuestionD

import java.util.*;
public class Main {
    static boolean check(String s){
            String t =new StringBuffer(s).reverse().toString();
            return s.equals(t);
        }
        public static void main(String[] args) {
            Scanner cin = new Scanner(System.in);
            //TODO
            while(cin.hasNext()){
                String s =cin.next();
                if(check(s)){
                    System.out.println("Y");
                }else{
                    System.out.println("N");
                }
            }
            cin.close();
        }
}

使用stringbuffer中的reverse事半功倍，string 转为stringbuffer 直接new stringbuffer(str) ，stringbuffer转为str使用tostring（）函数

QuestionE

import java.util.*;
public class Main {
	public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        while(cin.hasNextLine()){
            String str = cin.nextLine();
            System.out.println(str.toUpperCase());
        }
        cin.close();
    }
}

使用string字符串的toUppercase大写转为小写函数即可

QuestionF

import java.util.*;
public class Main {
	 public static void main(String[] args) {
        Scanner cn = new Scanner(System.in);
        String strA = cn.nextLine();
        String strB = cn.nextLine();
        System.out.println(getDistance(strA,strB));
        cn.close();
    }
    public static int getDistance(String strA, String strB){
        if (strA.equals(strB)) {//若两个字符串相同，返回0
            return 0;
        }
        int lengthA=strA.length();
        int lengthB=strB.length();
        int length=Math.max(lengthA,lengthB);//找到两个字符串长度最大值定义，二维数组的长度
        int array[][]=new int[length+1][length+1];//申请一个二维数组，存储转移矩阵
        for(int i=0;i<=length;i++){//边界条件初始化
            array[i][0]=i;
        }
        for(int j=0;j<=length;j++){
            array[0][j]=j;
        }
        for(int i=1;i<=lengthA;i++){//状态转移方程
            for(int j=1;j<=lengthB;j++){
                array[i][j]=min(array[i-1][j]+1,
                                array[i][j-1]+1,
                                array[i-1][j-1]+(strA.charAt(i-1)==strB.charAt(j-1)?0:1));
            }
        }
        return array[lengthA][lengthB];
    }
   //取三个数中的最小值
    public static int  min(int a,int b, int c){
        return Math.min(Math.min(a,b),c);
    }
}

使用动态规划。

QuestionG

import java.util.*;
public class Main {
  static int getmax(String str){
        int sum=65;
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)>sum)
                sum=str.charAt(i);
        }
        return sum;
    }
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        while(cin.hasNextLine()){
            String str = cin.nextLine();
            int k =getmax(str);
            for(int i=0;i<str.length();i++){
                if(str.charAt(i) == k)
                    System.out.print(str.charAt(i)+"(max)");
                else
                    System.out.print(str.charAt(i));
            }
            System.out.println();
        }
        cin.close();
    }
}

找到最大字符，这里字符的比较使用的asii码，A表示65最小，小写a97最小，找到后，将字符串进行遍历输出，遇到最大字符时，再其后输出max即可

QuestionH

import java.util.*;
public class Main {
 public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        int array[] = new int[27];
        while(cin.hasNextLine()){
            String str = cin.nextLine();
            boolean key=false;
            for(int i=0;i<str.length();i++){
                if(str.charAt(i)=='a'||str.charAt(i)=='A')
                    array[0]++;
                if(str.charAt(i)=='b'||str.charAt(i)=='B')
                    array[1]++;
                if(str.charAt(i)=='c'||str.charAt(i)=='C')
                    array[2]++;
                if(str.charAt(i)=='d'||str.charAt(i)=='D')
                    array[3]++;
                if(str.charAt(i)=='e'||str.charAt(i)=='E')
                    array[4]++;
                if(str.charAt(i)=='f'||str.charAt(i)=='F')
                    array[5]++;
                if(str.charAt(i)=='g'||str.charAt(i)=='G')
                    array[6]++;
                if(str.charAt(i)=='h'||str.charAt(i)=='H')
                    array[7]++;
                if(str.charAt(i)=='i'||str.charAt(i)=='I')
                    array[8]++;
                if(str.charAt(i)=='j'||str.charAt(i)=='J')
                    array[9]++;
                if(str.charAt(i)=='k'||str.charAt(i)=='K')
                    array[10]++;
                if(str.charAt(i)=='l'||str.charAt(i)=='L')
                    array[11]++;
                if(str.charAt(i)=='m'||str.charAt(i)=='M')
                    array[12]++;
                if(str.charAt(i)=='n'||str.charAt(i)=='N')
                    array[13]++;
                if(str.charAt(i)=='o'||str.charAt(i)=='O')
                    array[14]++;
                if(str.charAt(i)=='p'||str.charAt(i)=='P')
                    array[15]++;
                if(str.charAt(i)=='q'||str.charAt(i)=='Q')
                    array[16]++;
                if(str.charAt(i)=='r'||str.charAt(i)=='R')
                    array[17]++;
                if(str.charAt(i)=='s'||str.charAt(i)=='S')
                    array[18]++;
                if(str.charAt(i)=='t'||str.charAt(i)=='T')
                    array[19]++;
                if(str.charAt(i)=='u'||str.charAt(i)=='U')
                    array[20]++;
                if(str.charAt(i)=='v'||str.charAt(i)=='V')
                    array[21]++;
                if(str.charAt(i)=='w'||str.charAt(i)=='W')
                    array[22]++;
                if(str.charAt(i)=='x'||str.charAt(i)=='X')
                    array[23]++;
                if(str.charAt(i)=='y'||str.charAt(i)=='Y')
                    array[24]++;
                if(str.charAt(i)=='z'||str.charAt(i)=='Z')
                    array[25]++;
                if(str.charAt(i)=='#')
                    key=true;
            }
            if(key)
                break;;
        }
            System.out.println("a "+array[0]);
            System.out.println("b "+array[1]);
            System.out.println("c "+array[2]);
            System.out.println("d "+array[3]);
            System.out.println("e "+array[4]);
            System.out.println("f "+array[5]);
            System.out.println("g "+array[6]);
            System.out.println("h "+array[7]);
            System.out.println("i "+array[8]);
            System.out.println("j "+array[9]);
            System.out.println("k "+array[10]);
            System.out.println("l "+array[11]);
            System.out.println("m "+array[12]);
            System.out.println("n "+array[13]);
            System.out.println("o "+array[14]);
            System.out.println("p "+array[15]);
            System.out.println("q "+array[16]);
            System.out.println("r "+array[17]);
            System.out.println("s "+array[18]);
            System.out.println("t "+array[19]);
            System.out.println("u "+array[20]);
            System.out.println("v "+array[21]);
            System.out.println("w "+array[22]);
            System.out.println("x "+array[23]);
            System.out.println("y "+array[24]);
            System.out.println("z "+array[25]);
        cin.close();
    }
}

使用数组array存储字母的个数，读取多条数据使用while（cin.hasNextLine（））即可。

QuestionI

import java.util.*;
public class Main {
 public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        int m=cin.nextInt();
        for(int i=0;i<m;i++){
            String str = cin.next();
//            StringBuilder strb = new StringBuilder(str);
            for(int j=0;j<str.length();j++){
                if(str.charAt(j)>='a'&&str.charAt(j)<='z'){
                  System.out.print((char)(str.charAt(j)-32));
                }
                if(str.charAt(j)>='A'&&str.charAt(j)<='Z'){
                    System.out.print((char)(str.charAt(j)+32));
                }
            }
           System.out.println();
        }
        cin.close();
    }
}

简单，没啥好说的

QuestionJ

import java.util.*;
public class Main {
	public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        String key[] = new String[16];
        key[0]="0000";
        key[1]="0001";
        key[2]="0010";
        key[3]="0011";
        key[4]="0100";
        key[5]="0101";
        key[6]="0110";
        key[7]="0111";
        key[8]="1000";
        key[9]="1001";
        key[10]="1010";
        key[11]="1011";
        key[12]="1100";
        key[13]="1101";
        key[14]="1110";
        key[15]="1111";
        while(cin.hasNextLine()){
            String str =cin.nextLine();
            for(int i=0;i<str.length();i++){
                if(str.charAt(i)=='0')
                    System.out.print(key[0]);
                if(str.charAt(i)=='1')
                    System.out.print(key[1]);
                if(str.charAt(i)=='2')
                    System.out.print(key[2]);
                if(str.charAt(i)=='3')
                    System.out.print(key[3]);
                if(str.charAt(i)=='4')
                    System.out.print(key[4]);
                if(str.charAt(i)=='5')
                    System.out.print(key[5]);
                if(str.charAt(i)=='6')
                    System.out.print(key[6]);
                if(str.charAt(i)=='7')
                    System.out.print(key[7]);
                if(str.charAt(i)=='8')
                    System.out.print(key[8]);
                if(str.charAt(i)=='9')
                    System.out.print(key[9]);
                if(str.charAt(i)=='A')
                    System.out.print(key[10]);
                if(str.charAt(i)=='B')
                    System.out.print(key[11]);
                if(str.charAt(i)=='C')
                    System.out.print(key[12]);
                if(str.charAt(i)=='D')
                    System.out.print(key[13]);
                if(str.charAt(i)=='E')
                    System.out.print(key[14]);
                if(str.charAt(i)=='F')
                    System.out.print(key[15]);
            }
            System.out.println();
        }
        cin.close();
    }
}

我这里使用的一个笨方法，0-f十六进制，对应的二进制使用数组存储着，对于样例输入，直接输出对应的输出。

LatsQuestion

import java.util.Scanner;
import java.util.regex.Pattern;
//*
// 没考虑ip为空的情况，写了很久*/
public class last {
    public static boolean isInteger(String str) {
        if(str == null)
            return false;
        Pattern pattern = Pattern.compile("^(([0-9]|([1-9]\\d)|(1\\d\\d)|(2([0-4]\\d|5[0-5]))))$");
        return pattern.matcher(str).matches();
    }
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        //TODO
        while(cin.hasNextLine()){
            String str = cin.nextLine();
            if(str.equals("End of file"))
                break;
            String s[] =str.split("\\.");
            boolean k = true;
            if(s.length<4)
                k=false;
            for(int i=0;i<s.length;i++){
                if(!isInteger(s[i]))
                    k=false;
            }
            if(k)
                System.out.println("Y");
            else
                System.out.println("N");
        }
        cin.close();
    }
}

将一个ip，通过.使用split函数进行分隔，对分隔后的字符串数组中每一个字符串进行判读，看其是否符号即可。这里注意一点，就是分割后的字符串数组是否长度等于4，如果不等于4，那就根本不是一个ip地址

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原始发表：2021-05-10)，如有侵权请联系 cloudcommunity@tencent.com 删除

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