Kjh 3주차

[hannahf97]

양부터 다시 시작하겠습니다.

import java.io.BufferedReader;
import java.io.IOException;
import java.util.StringTokenizer;

public class Main{
    static int R,C;
    static char[][] maps;
    static boolean[][] visited;
    static int dx[] = {1,0,-1,0};
    static int dy[] = {0,1,0,-1};
    static Queue<int[]> queue = new LinkedList<>();
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        R = Integer.parseInt(st.nextToken());
        C = Integer.parseInt(st.nextToken());
        visited =new boolean[R][C];
        maps = new char[R][C];
        
        int vcount = 0;
        int ocount =0;
        for(int i=0; i<R; i++){
            String s = br.readLine();
            for(int j=0; j<C; j++){
                char x = s.charAt(j);
                maps[i][j] = x;


            }
        }


        for(int i=0; i<R; i++){
            for(int j=0; j<C; j++){
                if(!visited[i][j] && maps[i][j] == 'V'){
                    dfs(i,j);
                }
            }
        }
}

    public static void dfs(int x ,int y){
        visited[x][y] = true;
        int ocount =0;
        int vcount =0;
        queue.add(new int[]{x,y});
        while(!queue.isEmpty()){
            int[] now = queue.poll();
            int nowX = now[0];
            int nowY = now[1];

            for(int i=0; i<4; i++){
                int nX = nowX + dx[i];
                int nY = nowY + dy[i];
                
                if(nX >=0 && nX < R && nY >=0 && nY < C){
                    if(maps[nX][nY] == 'V' && !visited[nX][nY]){
                        queue.add(new int[]{nX,nY});
                        vistied[nX][nY] = true;
                        vcount +=1;
                    }
                    else if(maps[nX][nY] == '#'){
                        continue;
                    }
                    else if(maps[nX][nY] == '.' && !visited[nX][nY]){
                        queue.add(new int[]{nX,nY});
                        visited[nX][nY] = true;
                    }
                    else if(maps[nX][nY] == 'O'){
                        ocount += 1;
                    }
                }

            }
        }
    }
}

[hannahf97]

바이러스

예전에 풀었던 문제라 쉬웠다
bfs지만, queue를 사용하지 않고 재귀를 통해 풀었다.

import java.io.BufferedReader;
import java.io.IOException;
import java.util.StringTokenizer;
import java.util.*;
import java.io.*;
public class Main{
    static int n,m;
    static  ArrayList<Integer>[] arrayList;
    static boolean[] visited;
    static int count=0;
    public static void main(String[] args)throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      
        n = Integer.parseInt(br.readLine()); //컴퓨터 수
        m = Integer.parseInt(br.readLine()); //컴퓨터 번호 쌍
        arrayList = new ArrayList[n+1];
        visited = new boolean[n+1];
        for(int i=1; i<=n; i++){
            arrayList[i] = new ArrayList<Integer>();
        }
        for(int i=0; i<m; i++){
            StringTokenizer st = new StringTokenizer(br.readLine());
            int x = Integer.parseInt(st.nextToken());
            int y = Integer.parseInt(st.nextToken());
            arrayList[x].add(y);
            arrayList[y].add(x);
        }
        bfs(1);
        System.out.println(count);
    }
    public static void bfs(int num){
        visited[num] = true;
        for(int x : arrayList[num]){
            if(!visited[x]){
                count+=1;
                bfs(x);
            }
        }
    }
}

[hannahf97]

경로 찾기

다른 사람꺼 참고 하긴 했는데 n^3제곱으로 풀었는데 다른 방법 없는지 고민해봐야겠다.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.StringTokenizer;
public class Main{
    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 n = Integer.parseInt(br.readLine());
        int[][] arr = new int[n][n];
        
        for(int i=0; i<n; i++){
            StringTokenizer st = new StringTokenizer(br.readLine());
            for(int j=0; j<n; j++){
                arr[i][j] = Integer.parseInt(st.nextToken());
                
            }
        }
        
        for(int k=0; k<n; k++){
            for(int i=0; i<n; i++){
                for(int j=0; j<n; j++){
                    if(arr[i][k] ==1 && arr[k][j] == 1){
                        arr[i][j] =1;
                    }
                }
            }
        }
        
        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");
        }
        
        bw.write(sb.toString());
        bw.flush();
        bw.close();
        br.close();
    }
}

[hannahf97]

트리의 부모찾기

parents 생각하는 부분이 어려웠다.

import java.util.*;
import java.io.*;
public class Main
{
    static boolean visited[];
    static int N;
    static ArrayList<Integer>[] arr;
   public static void main(String[] args) throws IOException{
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      N = Integer.parseInt(br.readLine());
      arr = new ArrayList[N+1];
      visited = new boolean[N+1];
      for(int i=1; i<N+1; i++){
          arr[i] = new ArrayList();
      }
      
      for(int i=0; i<N-1; i++){
        StringTokenizer st = new StringTokenizer(br.readLine());
        int a = Integer.parseInt(st.nextToken());
        int b = Integer.parseInt(st.nextToken());
        
        arr[a].add(b);
        arr[b].add(a);
      }
      
      int[] parents = new int[N+1];
      
      dfs(parents, 1,0);
      
      for(int j=2; j<=N; j++) System.out.println(parents[j]);
      
   }
   public static void dfs(int[] parents, int start,int parent){
       parents[start] = parent; // 1부터 시작하기 때문에 1은 먼저 루트로 만들어준다
       for(int x: arr[start]){ 
           if(x != parent){
               dfs(parents, x, start); //1을 통해 찾은 다음것인기 때문에 1이 부모가된다 
               
           }
       }
   }
}

[hannahf97]

나이트의 이동

class 만드는것 참고해서 만들어보았습니다.

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

public class Main{
    static int l;
    static int dx[] = {-2,-1,1,2,-2,-1,1,2};
    static int dy[] = {1,2,2,1,-1,-2,-2,-1};
    static Point now, goal;
    public static void main(String[] args)throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int T = Integer.parseInt(br.readLine());


        ArrayList<Integer> arrlist = new ArrayList<>();

        for(int i=0; i<T; i++){
            l = Integer.parseInt(br.readLine());
            StringTokenizer st = new StringTokenizer(br.readLine());
           now = new Point(Integer.parseInt(st.nextToken()),
            							Integer.parseInt(st.nextToken()), 0);
             st = new StringTokenizer(br.readLine());
            goal = new Point(Integer.parseInt(st.nextToken()),
            							Integer.parseInt(st.nextToken()), 0);

            bfs(now);

        }


    }

    static void bfs(Point p){
        boolean visited[][] = new boolean[l][l];
        Queue<Point> queue = new LinkedList<>();
        visited[p.r][p.c] = true;
        queue.add(p);

        while(!queue.isEmpty()){
            Point tmp = queue.poll();
            int tmpX = tmp.r;
            int tmpY = tmp.c;
            int cnt = tmp.cnt;

            if(tmpX == goal.r && tmpY == goal.c){
                System.out.println(tmp.cnt);
                return;
            }
            for(int i=0; i<8; i++){
                int nx = tmpX + dx[i];
                int ny = tmpY + dy[i];

                if(nx >= 0 && nx < l && ny>= 0 && ny< l && !visited[nx][ny]){
                    queue.add(new Point(nx, ny, cnt+1));
                    visited[nx][ny] = true;
                }
            }
        }
    }

    static class Point{
        int r, c, cnt;

        public Point(int r, int c, int cnt){
            this.r = r;
            this.c = c;
            this.cnt = cnt;
        }
    }
}