구르는 돌에는 이끼가 끼지 않는다

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
	}

}

https://www.acmicpc.net/problem/11660

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;

/**
 * 구간합구하기5
 * @author ji
 *
 */
public class IntervalSum5 {
	
	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[] sizeSumCountStr = br.readLine().split(" ");
		int gridSize = Integer.valueOf(sizeSumCountStr[0]);
		int sumCount = Integer.valueOf(sizeSumCountStr[1]);

		int[][] numbersMap = new int[gridSize+1][gridSize+1];
		int[][] dp = new int[gridSize+1][gridSize+1];


		for (int i = 1; i <= gridSize; i++) {
			String[] points = br.readLine().split(" ");
			for (int j = 1; j <= gridSize; j++) {
				numbersMap[i][j] = Integer.valueOf(points[j-1]);
				//dp안에 0,0부터 특정 배열까지의 값들은 더해 놓음!!!
				dp[i][j] = dp[i-1][j] + dp[i][j-1] - dp [i-1][j-1] + numbersMap[i][j];

			}
		}

		for (int k = 1; k <= sumCount; k++) {
			String[] points = br.readLine().split(" ");
			int x1 = Integer.valueOf(points[0]);
			int y1 = Integer.valueOf(points[1]);
			int x2 = Integer.valueOf(points[2]);
			int y2 = Integer.valueOf(points[3]);

			//마지막 포인트 합에서 이전 포인트의 값들을 빼줌!!!
			int sum=dp[x2][y2] - dp[x2][y1-1] - dp[x1-1][y2] + dp[x1-1][y1-1];

			bw.write(String.valueOf(sum) + "\n");
		}

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

}