## 과제 : 백준 문제 풀이

목표 : 백준 문제를 풀어본다.

- [종이의 개수](https://www.acmicpc.net/problem/1780)
- [Z](https://www.acmicpc.net/problem/1074)
- [별 찍기 - 10](https://www.acmicpc.net/problem/2447)

## 과제 : 백준 문제 풀이 모범답안

### 종이의 개수

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

public class Main {
    static int[][] paper;
    static int minusOne = 0, zero = 0, one = 0;

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.nextLine());

        paper = new int[N][N];
        for (int i = 0; i < N; i++) {
            String[] row = sc.nextLine().split(" ");
            for (int j = 0; j < N; j++) {
                paper[i][j] = Integer.parseInt(row[j]);
            }
        }

        solve(0, 0, N);
        System.out.println(minusOne);
        System.out.println(zero);
        System.out.println(one);
    }

    public static void solve(int x, int y, int N) {
        if (check(x, y, N)) {
            if (paper[x][y] == -1) {
                minusOne++;
            } else if (paper[x][y] == 0) {
                zero++;
            } else {
                one++;
            }
            return;
        }

        int size = N / 3;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                solve(x + i * size, y + j * size, size);
            }
        }
    }

    public static boolean check(int x, int y, int N) {
        int value = paper[x][y];

        for (int i = x; i < x + N; i++) {
            for (int j = y; j < y + N; j++) {
                if (value != paper[i][j]) {
                    return false;
                }
            }
        }
        return true;
    }
}

### Z

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

public class Main {
    static int N, r, c;
    static int count = 0;

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);

        String[] input = sc.nextLine().split(" ");
        N = Integer.parseInt(input[0]);
        r = Integer.parseInt(input[1]);
        c = Integer.parseInt(input[2]);

        solve((int)Math.pow(2, N), 0, 0);
    }
    
    public static void solve(int size, int x, int y) {
        if (x == r && y == c) {
            System.out.println(count);
            return;
        }

        if (r < x + size && r >= x && c < y + size && c >= y) {
            int newSize = size / 2;
            solve(newSize, x, y);
            solve(newSize, x, y + newSize);
            solve(newSize, x + newSize, y);
            solve(newSize, x + newSize, y + newSize);
        } else {
            count += size * size;
        }
    }
}

### 별 찍기 - 10

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

public class Main {
    static char[][] arr;

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.nextLine());

        arr = new char[N][N];
        solve(0, 0, N, false);

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                sb.append(arr[i][j]);
            }
            sb.append('\n');
        }
        System.out.println(sb);
    }

    public static void solve(int x, int y, int N, boolean blank) {
        if (blank) {
            for (int i = x; i < x + N; i++) {
                for (int j = y; j < y + N; j++) {
                    arr[i][j] = ' ';
                }
            }
            return;
        }

        if (N == 1) {
            arr[x][y] = '*';
            return;
        }

        int size = N / 3;
        int count = 0;
        for (int i = x; i < x + N; i += size) {
            for (int j = y; j < y + N; j += size) {
                count++;
                if (count == 5) {
                    solve(i, j, size, true);
                } else {
                    solve(i, j, size, false);
                }
            }
        }
    }
}