[Coding Test] Baekjoon 알고리즘 기초 2/2 (1)

1. 500 - 브루트 포스

1-1. 일곱 난쟁이 (2309)

// dfs
import java.io.*;
import java.util.*;

public class P2309_일곱난쟁이 {
    static boolean[] visited;
    static int[] arr;
    static boolean bl;
    static int[] answer;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        answer = new int[7];
        visited = new boolean[9];
        arr = new int[9];
        for (int i = 0; i < 9; i++) {
            arr[i] = Integer.parseInt(br.readLine());
        }

        bl = false;
        dfs(0, 0, 0);

        Arrays.sort(answer);
        for (int i = 0; i < 7; i++) {
            bw.write(answer[i] + "\n");
        }

        bw.flush();
        bw.close();
        br.close();
    }

    public static void dfs(int depth, int sum, int start) {
        if (bl) {
            return;
        }

        if (sum > 100) {
            return;
        }

        if (depth == 7) {
            if (sum == 100) {
                int index = 0;
                for (int i = 0; i < 9; i++) {
                    if (visited[i]) {
                        answer[index] = arr[i];
                        index++;
                    }
                    bl = true;
                }
            }
            return;
        }

        for (int i = start; i < 9; i++) {
            if (!visited[i]) {
                visited[i] = true;
                dfs(depth + 1, sum + arr[i], i);
                visited[i] = false;
            }
        }
    }
}

// 구현
import java.io.*;
import java.util.*;

public class P2309_일곱난쟁이 {
    static int[] arr;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        arr = new int[9];
        int sum = 0;
        for (int i = 0; i < 9; i++) {
            arr[i] = Integer.parseInt(br.readLine());
            sum += arr[i];
        }

        Arrays.sort(arr);
        int x = -1;
        int y = -1;
        for (int i = 0; i < arr.length - 1; i++) {
            for (int j = i + 1; j < arr.length; j++) {
                if (sum - arr[i] - arr[j] == 100) {
                    x = i;
                    y = j;
                }
            }
        }

        for (int i = 0; i < arr.length; i++) {
            if (i == x || i == y) {
                continue;
            }

            bw.write(arr[i] + "\n");
        }

        bw.flush();
        bw.close();
        br.close();
    }
}

2. 510 - 브루트 포스 (N과 M)

2-1. N과 M 1 (15649)

import java.io.*;
import java.util.*;

class NOTE {
    static int[] arr;
    static boolean[] visited;
    static int N, M;
    static StringBuilder sb = new StringBuilder();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        visited = new boolean[N + 1];
        arr = new int[M];
        dfs(0);

        bw.write(sb + "");

        bw.flush();
        bw.close();
        br.close();
    }

    public static void dfs(int depth) {
        if (depth == M) {
            for (int i : arr) {
                sb.append(i + " ");
            }
            sb.append("\n");
            return;
        }

        for (int i = 1; i <= N; i++) {
            if (!visited[i]) {
                visited[i] = true;
                arr[depth] = i;
                dfs(depth + 1);
                visited[i] = false;
            }
        }
    }
}

2-2. N과 M 2 (15650)

import java.io.*;
import java.util.*;

class NOTE {
    static int N, M;
    static int[] arr;
    static StringBuilder sb = new StringBuilder();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());

        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        arr = new int[M];

        for (int i = 1; i <= N; i++) {
            arr[0] = i;
            dfs(1, i);
        }

        bw.write(sb + "");

        bw.flush();
        bw.close();
        br.close();
    }

    public static void dfs(int depth, int start) {
        if (depth == M) {
            for (int i : arr) {
                sb.append(i + " ");
            }
            sb.append("\n");
            return;
        }

        for (int i = start + 1; i <= N; i++) {
            arr[depth] = i;
            dfs(depth + 1, i);
        }
    }
}

2-3. N과 M 3 (15651)

import java.io.*;
import java.util.*;

class NOTE {
    static int N, M;
    static int[] arr;
    static StringBuilder sb = new StringBuilder();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());

        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        arr = new int[M];

        dfs(0);

        bw.write(sb.toString() + "");

        bw.flush();
        bw.close();
        br.close();
    }

    public static void dfs(int depth) {
        if (depth == M) {
            for (int i : arr) {
                sb.append(i + " ");
            }
            sb.append("\n");
            return;
        }

        for (int i = 1; i <= N; i++) {
            arr[depth] = i;
            dfs(depth + 1);
        }
    }
}

2-4. N과 M 4 (15652)

import java.io.*;
import java.util.*;

class NOTE {
    static int N, M;
    static int[] arr;
    static StringBuilder sb = new StringBuilder();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());

        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        arr = new int[M];

        dfs(0, 1);

        bw.write(sb.toString() + "");

        bw.flush();
        bw.close();
        br.close();
    }

    public static void dfs(int depth, int start) {
        if (depth == M) {
            for (int i : arr) {
                sb.append(i + " ");
            }
            sb.append("\n");
            return;
        }

        for (int i = start; i <= N; i++) {
            arr[depth] = i;
            dfs(depth + 1, i);
        }
    }
}

3. 520 - 브루트 포스 - 순열

3-1. 다음 순열 (10972)

import java.io.*;
import java.util.*;

class P10972_다음순열 {
    static int N;
    static int[] arr;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        N = Integer.parseInt(br.readLine());
        st = new StringTokenizer(br.readLine());

        arr = new int[N];
        for (int i = 0; i < N; i++) {
            arr[i] = Integer.parseInt(st.nextToken());
        }

        if (isPrime()) {
            StringBuilder sb = new StringBuilder();
            for (int i : arr) {
                sb.append(i + " ");
            }
            sb.append("\n");
            bw.write(sb + "");
        } else {
            bw.write("-1\n");
        }

        bw.flush();
        bw.close();
        br.close();
    }

    public static boolean isPrime() {
        int i = arr.length - 1;
        while (i > 0 && arr[i - 1] > arr[i]) {
            i--;
        }
        if (i == 0) {
            return false;
        }

        int j = arr.length - 1;
        while (arr[i - 1] > arr[j]) {
            j--;
        }

        int temp = arr[i - 1];
        arr[i - 1] = arr[j];
        arr[j] = temp;

        j = arr.length - 1;
        while (i < j) {
            temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;

            i++;
            j--;
        }

        return true;
    }
}

4. 530 - 브루트 포스 - 재귀

4-1. 1, 2, 3 더하기 (9095)

import java.io.*;
import java.util.*;

class P9095_123더하기 {
    static int n;
    static int[] arr;
    static int answer;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int T = Integer.parseInt(br.readLine());

        for (int i = 0; i < T; i++) {
            n = Integer.parseInt(br.readLine());
            arr = new int[3];
            arr[0] = 1;
            arr[1] = 2;
            arr[2] = 3;

            answer = 0;
            dfs(0);
            bw.write(answer + "\n");
        }

        bw.flush();
        br.close();
        bw.close();
    }

    public static void dfs(int sum) {
        if (sum > n) {
            return;
        }

        if (sum == n) {
            answer++;
            return;
        }

        for (int i = 0; i < 3; i++) {
            dfs(sum + arr[i]);
        }
    }
}

5. 540 - 브루트 포스 - 비트마스크

5-1. 집합 (11723)

import java.io.*;
import java.util.StringTokenizer;

public class P11723_집합 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        int S = 0;
        int M = Integer.parseInt(br.readLine());

        for (int i = 0; i < M; i++) {
            st = new StringTokenizer(br.readLine());
            String str = st.nextToken();

            if (str.equals("all")) S = (1 << 21) - 1;
            else if (str.equals("empty")) S = 0;
            else {
                int num = Integer.parseInt(st.nextToken());
                switch (str) {
                    case "add":
                        S = S | (1 << num);
                        break;
                    case "remove":
                        S = S & ~(1 << num);
                        break;
                    case "check":
                        bw.write(((S & (1 << num)) != 0 ? 1 : 0) + "\n");
                        break;
                    case "toggle":
                        S = S ^ (1 << num);
                        break;
                }
            }
        }
        bw.close();
    }
}