코딩테스트 대비 (Array)

sua·2022년 9월 15일
CodingTest

자바(Java) 알고리즘 문제풀이

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1. 큰 수 출력하기

문제


풀이

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public ArrayList<Integer> solution(int n, int[] arr) {
        ArrayList<Integer> answer = new ArrayList<>();
        answer.add(arr[0]);
        for(int i = 1; i < n; i++) {
            if(arr[i] > arr[i - 1]) {
                answer.add(arr[i]);
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] arr = new int[n];

        for(int i = 0; i < n; i++) {
            arr[i] = kb.nextInt();
        }

        for(int x : T.solution(n, arr)) {
            System.out.print(x + " ");
        }
    }
}



2. 보이는 학생

문제


풀이

import java.util.Scanner;

public class Main {
    public int solution(int n, int[] arr) {
        int answer = 1, max = arr[0];
        
        for(int i = 1; i < n; i++) {
            if(arr[i] > max) {
                answer++;
                max = arr[i];
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] arr = new int[n];

        for(int i = 0; i < n; i++) {
            arr[i] = kb.nextInt();
        }

        System.out.print(T.solution(n, arr));
    }
}



3. 가위바위보

문제


풀이

import java.util.Scanner;

public class Main {
    public String solution(int n, int[] a, int[] b) {
        String answer = "";

        for(int i = 0; i < n; i++) {
            if(a[i] == b[i]) {
                answer += "D";
            } else if(a[i] == 1 && b[i] == 3) {
                answer += "A";
            } else if(a[i] == 2 && b[i] == 1) {
                answer += "A";
            } else if(a[i] == 3 && b[i] == 2) {
                answer += "A";
            } else {
                answer += "B";
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] a = new int[n];
        int[] b = new int[n];

        for(int i = 0; i < n; i++) {
            a[i] = kb.nextInt();
        }

        for(int i = 0; i < n; i++) {
            b[i] = kb.nextInt();
        }

        for(char x : T.solution(n, a, b).toCharArray()) {
            System.out.println(x);
        }
    }
}



4. 피보나치 수열

문제


풀이

import java.util.Scanner;

public class Main {
	/*
    public int[] solution(int n) {
        int[] answer = new int[n];
        answer[0] = 1;
        answer[1] = 1;
        
        for(int i = 2; i < n; i++) {
            answer[i] = answer[i - 2] + answer[i - 1];
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();

        for(int x : T.solution(n)) {
            System.out.print(x + " ");
        }
    }
    */
    public void solution(int n) {
        int a = 1, b = 1, c;
        System.out.print(a + " " + b + " ");
        for(int i = 2; i < n; i++) {
            c = a + b;
            System.out.println(c + " ");
            a = b;
            b = c;
        }
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();

        T.solution(n);
    }
}



5. 소수(에라토스테네스 체)

문제


풀이

import java.util.Scanner;

public class Main {
    public int solution(int n) {
        int answer = 0;
        int[] ch = new int[n + 1];

        for(int i = 2; i <= n; i++) {
            if(ch[i] == 0) {
                answer++;
                for(int j = i; j <= n; j = j + i) {
                    ch[j] = 1;
                }
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        System.out.println(T.solution(n));
    }
}



6. 뒤집은 소수

문제


풀이

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public boolean isPrime(int num) {
        if(num == 1) {
            return false;
        } 
        for(int i = 2; i < num; i++) {
            if(num % i == 0) {
                return false;
            }
        }
        return true;
    }

    public ArrayList<Integer> solution(int n, int[] arr) {
        ArrayList<Integer> answer = new ArrayList<>();

        for(int i = 0; i < n; i++) {
            int tmp = arr[i];
            int res = 0;
            while(tmp > 0) {
                int t = tmp % 10;
                res = res * 10 + t;
                tmp = tmp / 10;
            }

            if(isPrime(res)) {
                answer.add(res);
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] arr = new int[n];

        for(int i = 0; i < n; i++) {
            arr[i] = kb.nextInt();
        }

        for(int x : T.solution(n, arr)) {
            System.out.print(x + " ");
        }
    }
}



7. 점수계산

문제



풀이

import java.util.Scanner;

public class Main {
    public int solution(int n, int[] arr) {
        int answer = 0, cnt = 0;
        
        for(int i = 0; i < n; i++) {
            if(arr[i] == 1) {
                cnt++;
                answer += cnt;
            } else {
                cnt = 0;
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] arr = new int[n];

        for(int i = 0; i < n; i++) {
            arr[i] = kb.nextInt();
        }

        System.out.print(T.solution(n, arr));
    }
}



8. 등수구하기

문제


풀이

import java.util.Scanner;

public class Main {
    public int[] solution(int n, int[] arr) {
        int[] answer = new int[n];

        for(int i = 0; i < n; i++) {
            int cnt = 1;
            for(int j = 0; j < n; j++) {
                if(arr[j] > arr[i]) {
                    cnt++;
                }
                answer[i] = cnt;
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[] arr = new int[n];

        for(int i = 0; i < n; i++) {
            arr[i] = kb.nextInt();
        }

        for(int x : T.solution(n, arr)) {
            System.out.print(x + " ");
        }
    }
}



9. 격자판 최대합

문제


풀이

import java.util.Scanner;

public class Main {
    public int solution(int n, int[][] arr) {
        int answer = Integer.MIN_VALUE;
        int sum1, sum2;

        for(int i = 0; i < n; i++) {
            sum1 = sum2 = 0;
            for(int j = 0; j < n; j++) {
                sum1 += arr[i][j];
                sum2 += arr[j][i];
            }
            answer = Math.max(answer, sum1);
            answer = Math.max(answer, sum2);
        }
        
        sum1 = sum2 = 0;
        for(int i = 0; i < n; i++) {
            sum1 += arr[i][i];
            sum2 += arr[i][n - i - 1];
        }
        answer = Math.max(answer, sum1);
        answer = Math.max(answer, sum2);

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[][] arr = new int[n][n];

        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                arr[i][j] = kb.nextInt();
            }
        }

        System.out.print(T.solution(n, arr));
    }
}



10. 봉우리

문제


풀이

import java.util.Scanner;

public class Main {
    int[] dx = {-1, 0, 1, 0};
    int[] dy = {0, 1, 0, -1};

    public int solution(int n, int[][] arr) {
        int answer = 0;

        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                boolean flag = true;
                for(int k = 0; k < 4; k++) {
                    int nx = i + dx[k];
                    int ny = j + dy[k];
                    if(nx >= 0 && nx < n && ny >= 0 && ny < n && arr[nx][ny] >= arr[i][j]) {
                        flag = false;
                        break;
                    }
                }
                if(flag) {
                    answer++;
                }
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[][] arr = new int[n][n];

        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                arr[i][j] = kb.nextInt();
            }
        }

        System.out.print(T.solution(n, arr));
    }
}



11. 임시반장정하기

문제



풀이

import java.util.Scanner;

public class Main {
    public int solution(int n, int[][] arr) {
        int answer = 0, max = Integer.MIN_VALUE;

        for(int i = 1; i <= n; i++) {
            int cnt = 0;
            for(int j = 1; j <= n; j++) {
                for(int k = 1; k <= 5; k++) {
                    if(arr[i][k] == arr[j][k]) {
                        cnt++;
                        break;
                    }
                }
            }
            if(cnt > max) {
                max = cnt;
                answer = i;
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int[][] arr = new int[n + 1][6];

        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= 5; j++) {
                arr[i][j] = kb.nextInt();
            }
        }

        System.out.print(T.solution(n, arr));
    }
}



12. 멘토링

문제


풀이

import java.util.Scanner;

public class Main {
    public int solution(int n, int m, int[][] arr) {
        int answer = 0;

        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                int cnt = 0;
                for(int k = 0; k < m; k++) {
                    int pi = 0, pj = 0;
                    for(int s = 0; s < n; s++) {
                        if(arr[k][s] == i) {
                            pi = s;
                        }
                        if(arr[k][s] == j) {
                            pj = s;
                        }
                    }
                    if(pi < pj) {
                        cnt++;
                    }

                }
                if(cnt == m) {
                    answer++;
                }
            }
        }

        return answer;
    }

    public static void main(String[] args){
        Main T = new Main();
        Scanner kb = new Scanner(System.in);
        int n = kb.nextInt();
        int m = kb.nextInt();
        int[][] arr = new int[m][n];

        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {
                arr[i][j] = kb.nextInt();
            }
        }

        System.out.print(T.solution(n, m, arr));
    }
}
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