구르는 돌에는 이끼가 끼지 않는다

https://www.acmicpc.net/problem/2293

package com.ji.beakjoon.dp;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

/**
 * 동전1
 * @author ji
 *
 */
public class Coin1 {

	static int[] dp;
	static int[] coinTypes;
	public static void main(String[] args) throws IOException {
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		String[] condition = br.readLine().split(" ");
		int coinType = Integer.valueOf(condition[0]);
		int targetNum = Integer.valueOf(condition[1]);
		
		coinTypes = new int[coinType+1];
		dp = new int[targetNum + 1];
		dp[0] = 1;
		
		for(int i=1; i <= coinType; i++) {
			coinTypes[i] = Integer.valueOf(br.readLine());
			for(int j=coinTypes[i]; j <= targetNum; j++) {
				//dp 안에 각 동전 금액에 따라서 targetNumber가 되는 과정을 dp에 저장하여 처리
				dp[j] += dp[j - coinTypes[i]];
			}
		}
		
		bw.write(String.valueOf(dp[targetNum]));
		
		br.close();
		bw.flush();
		bw.close();
		
	}
	
}

https://www.acmicpc.net/problem/2468

package com.ji.beakjoon.dfs;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * 안전 영역 
 * @author ji
 *
 */
public class SafeZoneDfs {

	static int[][] safeZoneMap;//안전구역 정보
	static int safeZoneMapSize = 0; //안전구역 맵 크기
	static boolean[][] DFSisVisited;
	static List<Integer> list;//각 수위 경계값에 따른 결과 값 저장
	static int[] dx = {1, -1, 0, 0}; //상하좌우위아래
	static int[] dy = {0, 0, 1, -1}; 
	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

		safeZoneMapSize = Integer.valueOf(br.readLine()); // 행렬 가로 길이
		safeZoneMap = new int[safeZoneMapSize][safeZoneMapSize];
		DFSisVisited = new boolean[safeZoneMapSize][safeZoneMapSize];
		
		int max = 0;
		for (int i = 0; i < safeZoneMapSize; i++) {
			String[] complexGraphInfo = String.valueOf(br.readLine()).split(" ");
			for (int j = 0; j < safeZoneMapSize; j++) {
				safeZoneMap[i][j] = Integer.valueOf(complexGraphInfo[j]);
				if(max < safeZoneMap[i][j])
					max = safeZoneMap[i][j];
			}
		}
		
		list = new ArrayList<>();
		
		for(int depth=0; depth<=max ; depth++) {
			int cnt = 0; 
			for (int i = 0; i < safeZoneMapSize; i++) {
				for (int j = 0; j < safeZoneMapSize; j++) {
					if(safeZoneMap[i][j] > depth && !DFSisVisited[i][j]) {
						cnt++;
						dfs(i, j, depth);
					}
					
				}
			}
			
			//dfs 방문정보 초기화!!!!
			for(boolean a[]:DFSisVisited)
				Arrays.fill(a, false);
			list.add(cnt);
		}
		
		int maxResult = Collections.max(list);
		bw.write(String.valueOf(maxResult) );

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

	}

	public static void dfs(int x, int y, int depth) {
		DFSisVisited[x][y] = true;
		
		for(int i=0; i < 4; i++) {
			int nx = x + dx[i];
			int ny = y + dy[i];
			
			if(nx >=0 && ny >=0 && nx < safeZoneMap.length && ny< safeZoneMap.length) {
				if(safeZoneMap[nx][ny] > depth && !DFSisVisited[nx][ny])
					dfs(nx, ny, depth);
			}
			
		}

	}

}

https://www.acmicpc.net/problem/15653

package com.ji.beakjoon;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class MarbleEscape4_Study {
	
	static class Node{
		int r, c, time; 
		char type; 
		
		Node(int r, int c, char type, int time){
			this.r = r; 
			this.c = c;
			this.type =type; 
			this.time = time;
		}
	}
	
	static Queue<Node> q;
	static boolean[][][][] visited;
	static int[][] dir = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
	static char[][] map;
	static int blueR, blueC, redR, redC;
	static int N, M; 
	
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());

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

		q = new LinkedList<>();
		visited = new boolean[N][M][N][M];
		map = new char[N][M];

		for (int r = 0; r < N; ++r) {
			char[] line = br.readLine().toCharArray();
			for (int c = 0; c < M; ++c) {
				if (line[c] == 'R') {
					map[r][c] = '.';
					redR = r;
					redC = c;
					q.offer(new Node(r, c, line[c], 0));
				} else if (line[c] == 'B') {
					map[r][c] = '.';
					blueR = r;
					blueC = c;
					q.offer(new Node(r, c, line[c], 0));
				} else {
					map[r][c] = line[c];
				}
			}
		}

		visited[redR][redC][blueR][blueC] = true;

		System.out.println(bfs());
			
	}

	private static int bfs() {
		while (!q.isEmpty()) {
			Node blue, red;
			if (q.peek().type == 'B') {
				blue = q.poll();
				red = q.poll();
			} else {
				red = q.poll();
				blue = q.poll();
			}

			boolean blueInHole, redInHole, afterRed;
			int bcr, bcc, rcr, rcc;
			int bnr, bnc, rnr, rnc;
			for (int d = 0; d < 4; ++d) {
				blueInHole = redInHole = afterRed = false;
				bcr = blue.r;
				bcc = blue.c;
				rcr = red.r;
				rcc = red.c;

				// 파랑 구슬 이동
				while (true) {
					bnr = bcr + dir[d][0];
					bnc = bcc + dir[d][1];
					if (bnr == rcr && bnc == rcc)
						afterRed = true;
					if (map[bnr][bnc] == '#')
						break;
					if (map[bnr][bnc] == 'O') {
						blueInHole = true;
						break;
					}
					bcr = bnr;
					bcc = bnc;
				}

				// 빨강 구슬 이동
				while (true) {
					rnr = rcr + dir[d][0];
					rnc = rcc + dir[d][1];
					if (map[rnr][rnc] == '#')
						break;
					if (map[rnr][rnc] == 'O') {
						redInHole = true;
						break;
					}
					rcr = rnr;
					rcc = rnc;
				}

				// 파란구슬이 들어갔을 때
				if (blueInHole)
					continue;
				// 빨간구슬이 들어갔을 때
				if (redInHole)
					return red.time + 1;

				// 구슬이 겹쳤을 때
				if (bcr == rcr && bcc == rcc) {
					// 빨간구슬 다음에 파란구슬이 올 때
					if (afterRed) {
						bcr -= dir[d][0];
						bcc -= dir[d][1];
						// 파란구슬 다음에 빨간구슬이 올 때
					} else {
						rcr -= dir[d][0];
						rcc -= dir[d][1];
					}
				}
				// 방문체크
				if (visited[rcr][rcc][bcr][bcc])
					continue;
				visited[rcr][rcc][bcr][bcc] = true;

				q.offer(new Node(bcr, bcc, 'B', blue.time + 1));
				q.offer(new Node(rcr, rcc, 'R', red.time + 1));
			}
		}

		return -1;
	}

}