구르는 돌에는 이끼가 끼지 않는다

https://www.acmicpc.net/problem/17836

package com.ji.beakjoon.bfs;

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

public class SavePrincess {
	static int N, M, T;
	static int map[][];
	static int dr[] = {-1, 1, 0, 0};
	static int dc[] = {0, 0, -1, 1};
	static int ret;
	static class Pair{
		int r,c,time;
		int item;
		
		public Pair(int r, int c,  int item, int time) {
			super();
			this.r = r;
			this.c = c;
			this.time = time;
			this.item = item;
		}
		
	}
	
	static ArrayList<Pair> list;
	
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		N = Integer.valueOf(st.nextToken());
		M = Integer.valueOf(st.nextToken());
		T = Integer.valueOf(st.nextToken());
		map = new int[N][M];
		ret = 0;
		for(int i=0; i<N;i++) {
			st = new StringTokenizer(br.readLine());
			for(int j=0; j<M; j++) {
				map[i][j] = Integer.valueOf(st.nextToken());
			}
		}
		bfs();
		if(ret!=0)
			System.out.println(ret);
		else
			System.out.println("Fail");
	}
	private static void bfs() {
		boolean visit[][][] = new boolean[2][N][M]; //검 유무, 세로, 가로
		Queue<Pair> q = new LinkedList<>();
		q.add(new Pair(0,0,0,0));
		visit[0][0][0] = true;
		while(!q.isEmpty()) {
			Pair cur = q.poll();
			if(cur.r == N-1 && cur.c == M-1) {
				if(cur.time <= T)
					ret = cur.time;
				break;
			}
			if(cur.time > T)
				break; 
			for(int i=0; i<4; i++) {
				int nr = cur.r+dr[i];
				int nc = cur.c+dc[i];
				if(nr<0||nc<0||nr>=N||nc>=M||visit[cur.item][nr][nc]) continue;
				
				//방문하지 않고 아이템이 없는 경우
				if(cur.item==0) {
					
					if(map[nr][nc] == 0) {
						visit[0][nr][nc] = true;
						q.add(new Pair(nr,nc,0, cur.time +1));
					}else if(map[nr][nc]==2) {
						visit[1][nr][nc]=true;
						q.add(new Pair(nr,nc, 1, cur.time+1));
					}
					
				}else {//방문하지 않고 아이템이 있는 경우 벽 뚫기 가능
					if(map[nr][nc]==1||map[nr][nc]==0) {
						visit[1][nr][nc]=true;
						q.add(new Pair(nr,nc, 1, cur.time+1));
					}
				}
				
			}
		}
		
	}

}

https://www.acmicpc.net/problem/2156

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;

/**
 * 포도주 시식
 * @author ji
 *
 */
public class WineTasting {

	static Integer[] dp;
	static int[] wineAmountArr;

	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 wineCount = Integer.valueOf(br.readLine());
		
		wineAmountArr = new int[wineCount+1];
		dp = new Integer[wineCount+1];
		
		for(int i=1; i<wineCount+1; i++) {
			wineAmountArr[i] = Integer.valueOf(br.readLine());
		}
		dp[0] = 0;
		dp[1] = wineAmountArr[1];
		
		if(wineCount > 1) {
			dp[2] = wineAmountArr[1] + wineAmountArr[2];
		}

		bw.write(String.valueOf(recur(wineCount)));
		
		//Bottom-Up
//		dp[1] = wineAmountArr[1];
//		if (wineCount > 1) {
//			dp[2] = wineAmountArr[1] + wineAmountArr[2];
//		}
//		for (int i = 3; i <= wineCount; i++) {
//			dp[i] = Math.max(dp[i - 1], Math.max(dp[i - 2] + wineAmountArr[i], dp[i - 3] + wineAmountArr[i - 1] + wineAmountArr[i]));
//		}
//		System.out.println(dp[wineCount]);
		
		br.close();
		bw.flush();
		bw.close();

	}
	
	//Top-Down
	static int recur(int N) {
		
		//각 노드의 이전의 최대값과 비교, 조합 가능한 최대값을 저장
		if(dp[N] == null) {
			dp[N] = Math.max(
										Math.max( recur(N - 2),  recur(N - 3) + wineAmountArr[N - 1] ) 
										+ wineAmountArr[N]
										, 
										recur(N - 1)
									 );
		}
		
		return dp[N];
	}
	

}

https://www.acmicpc.net/problem/2667

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.Collections;
import java.util.List;

/**
 * 단지번호붙이기
 * @author ji
 *
 */
public class ComplexNum {

	static int complexMapSize = 0; //단지 지도 크기
	static int homeCnt = 0;//각 단지 집수
	static List<Integer> complexList = new ArrayList<Integer>(); //단지 크기 정보

	public static void main(String[] args) throws IOException {

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

		complexMapSize = Integer.valueOf(br.readLine()); // 행렬 가로 길이
		int[][] complexGraph = new int[complexMapSize + 1][complexMapSize + 1];

		for (int i = 0; i < complexMapSize; i++) {
			String[] complexGraphInfo = String.valueOf(br.readLine()).split("");
			for (int j = 0; j < complexMapSize; j++)
				complexGraph[i][j] = Integer.valueOf(complexGraphInfo[j]);
		}

		for (int j = 0; j < complexMapSize; j++) {
			for (int i = 0; i < complexMapSize; i++) {
				if (complexGraph[i][j] == 1) {
					homeCnt = 0;
					dfs(complexGraph, i, j);
					complexList.add(homeCnt);
				}
			}
		}

		Collections.sort(complexList);

		bw.write(String.valueOf(complexList.size()) + "\n");
		for (int cnt : complexList)
			bw.write(String.valueOf(cnt) + "\n");

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

	}

	static void dfs(int[][] graph, int i, int j) {
		int m = complexMapSize, n = complexMapSize;

		if (i < 0 || i >= m || j < 0 || j >= n || graph[i][j] != 1)
			return;

		//첫 단지 시작 이외 접근한 집은 -1처리
		graph[i][j] = -1;
		homeCnt++;

		dfs(graph, i - 1, j);// 위
		dfs(graph, i + 1, j);// 아래
		dfs(graph, i, j - 1);// 왼쪽
		dfs(graph, i, j + 1);// 오른쪽
	}

}