섹션1. String(문자열)

1. 문자찾기

 

 

 

 

import java.util.Scanner;
public class Main {
    public int solution(String str, char t){
        int answer=0;
        str=str.toUpperCase();
        t=Character.toUpperCase(t);
        for(int i=0; i<str.length(); i++){
            if(str.charAt(i)==t)
                answer++;
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str = kb.next();
        char c = kb.next().charAt(0);
        System.out.print(T.solution(str,c));
    }
}

 

 

 

2. 대소문자 변환

 

 

 

import java.util.*;
public class Main {
    public String solution(String str){
        String answer="";
        for(char x : str.toCharArray()){
            if(Character.isLowerCase(x))
                answer+=Character.toUpperCase(x);
            else
                answer+=Character.toLowerCase(x);
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str = kb.next();
        System.out.print(T.solution(str);
    }
}

 

 

 

3. 문장 속 단어 ( indextOf(), substring() )

 

 

 

import java.util.*;
public class Main {
    public String solution(String str){
        String answer="";
        int m=Integer.MIN_VALUE; // 작은 값으로 초기화
        String[] s=str.split(" "); // split 
        for(String x : s){
            int len=x.length();
            if(len>m){ // 최댓값 알고리즘
                m=len;
                answer=x;
            }
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str = kb.nextLine();
        System.out.print(T.solution(str);
    }
}

 

 

 

4. 단어 뒤집기(StringBuilder 이용법 또는 직접뒤집기 )

 

 

 

import java.util.*;
public class Main {
    public ArrayList<String> solution(int n, String[] str){
        ArrayList<String> answer=new ArrayList<>();
        for(String x:str){
            String tmp=new StringBuilder(x).reverse().toString();
            answer.add(tmp);
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
       String[] str=new String[n];
       for(int i=0; i<n; i++){
           str[i]=kb.next();
       }
       for(String x:T.solution(n,str)){
           System.out.println(x);
       }
    }
}

 

 

 

5. 특정 문자 뒤집기( toCharArray() )

 

 

import java.util.*;
public class Main {
    public String solution(String str){
        String answer;
        char[] s=str.toCharArray();
        int lt=0;
        int rt=str.length()-1;
        while(lt<rt) {
            if(!Character.isAlphabetic(s[lt])) // 알파벳이 아닐때
                lt++;
            else if(!Character.isAlphabetic(s[rt])) // 알파벳이 아닐때
                rt++;
            else { // 알파벳이면
                char tmp=s[lt];
                s[lt]=s[rt];
                s[rt]=tmp;
                lt++;
                rt--;
            }
        }
        answer=String.valueOf(s); // line5 : 바꿨던 s 배열을 다시 String화
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.next();
        System.out.print(T.solution(str));
        }
}

 

 

6. 중복문자제거

 

 

 

import java.util.*;
public class Main {
    public String solution(String str){
        String answer="";
        for(int i=0; i<str.length(); i++){
            if(str.indexOf(str.charAt(i))==i)
                answer+=str.charAt(i);
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.next();
        System.out.print(T.solution(str));
    }
}

 

 

 

7. 회문문자열

 

 

solution1

import java.util.*;
public class Main {
    public String solution(String str){
        String answer="No"; // str=정방향 tmp=역방향
        String tmp=new StringBuilder(str).reverse().toString();
        if(str.equalsIgnoreCase(tmp)) // 대소문자 구분 없이 같은지 확인
            answer="YES";

        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.next();
        System.out.print(T.solution(str));
    }
}

 

solution2

import java.util.*;
public class Main {
    public String solution(String str){
        String answer="YES";
        str=str.toUpperCase();
        int len=str.length();
        for(int i=0; i<len/2; i++){
            if(str.charAt(i)!=str.charAt(len-i-1))
                return "No";
        }
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.next();
        System.out.print(T.solution(str));
    }
}

 

 

8. 팰린드롬( replaceAll 정규식이용 )

 

 

 

import java.util.*;
public class Main {
    public String solution(String s){
       String answer="NO";
       s=s.toUpperCase().replaceAll("[^A-Z]",""); //A-Z이 아닌것은 "" 대체
       String tmp=new StringBuilder(s).reverse().toString();
       if(s.equals(tmp)) answer="YES";
       return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.nextLine();
        System.out.print(T.solution(str));
    }
}

 

 

 

9. 숫자만 추출

 

 

 

import java.util.*;
public class Main {
    public int solution(String s){
       String answer="";
       for(char x : s.toCharArray()){
            if(Character.isDigit(x))
                answer+=x;
       }
       return Integer.parseInt(answer);
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.nextLine();
        System.out.print(T.solution(str));
    }
}

 

 

 

10. 문자거리

 

 

 

import java.util.*;
public class Main {
    public int[] solution(String s, char t){
        int[] answer=new int[s.length()];
        int p=1000;
        for(int i=0; i<s.length(); i++){
            if(s.charAt(i)==t){
                p=0;
                answer[i]=p;
            }
            else{
                p++;
                answer[i]=p;
            } // 왼쪽으로부터 떨어진 거리
        }
        p=1000;
        for(int i=s.length()-1; i>=0; i--){
            if(s.charAt(i)==t)
                p=0;
            else{
                p++;
                answer[i]=Math.min(answer[i],p); // 기존값과 p값중 더 작은것
            }
        } // 오른쪽부터 떨어진 거리
        return answer;
    }
    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str=kb.next();
        char c=kb.next().charAt(0); // 문자 한개 읽을때
        for(int x : T.solution(str,c)){
            System.out.print(x+" ");
        }
    }
}

 

 

 

 

11. 문자열 압축

 

 

import java.util.*;
class Main {
    public String solution(String s){
        String answer="";
        s=s+" ";
        int cnt=1;
        for(int i=0; i<s.length()-1; i++){
            if(s.charAt(i)==s.charAt(i+1))
                cnt++;
            else {
                answer += s.charAt(i);
                if (cnt > 1)
                    answer += String.valueOf(cnt);
                cnt = 1;
            }
        }
        return answer;
    }
    public static void main(String[] args) {
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        String str = kb.next();
        System.out.print(T.solution(str));
    }
}

 

 

 

12. 암호 ( replace(), parseInt(string, 2) )

 

 

 

 

import java.util.*;
class Main {
    public String solution(int n,String s){
        String answer="";
        for(int i=0; i<n; i++){
            String tmp=s.substring(0,7).replace('#','1').replace('*','0');
            int num=Integer.parseInt(tmp,2);
            answer+=(char)num;
            s=s.substring(7);
        }
        return answer;
    }
    public static void main(String[] args) {
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        String str=kb.next();
        System.out.println(T.solution(n, str));
    }
}