[PS] RGB거리 (백준 1148번)

쉬운 편에 속하는 DP 문제인 것 같은데, 아주 아주 약간(?)의 발상이 필요한 문제였다.

필기를 통해 충분히 계산하고 코드 작성을 시작하자!

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

/* BOJ no.1149 - RGB거리 (DP) */
public class Main {

    static int N;
    static int[] costOfLastRed = new int[1001];
    static int[] costOfLastGreen = new int[1001];
    static int[] costOfLastBlue = new int[1001];
    static int totalCost;
    
    public static void main(String[] args) {
        inputAndCalculate();
        printResult();
    }
    
    static void printResult() {
        System.out.println(totalCost);
    }

    static void inputAndCalculate() {
        Reader reader = new Reader();
        N = reader.readInt();
        int size = N+1;
        int redCostOfIdx = 0;
        int greenCostOfIdx = 0;
        int blueCostOfIdx = 0;
        int beforeIdx = -1;
        for (int idx = 1; idx < size; idx++) {
            if (idx == 1) {
                costOfLastRed[idx] = reader.readInt();
                costOfLastGreen[idx] = reader.readInt();
                costOfLastBlue[idx] = reader.readInt();
                continue;
            }
            
            beforeIdx = idx - 1;
            redCostOfIdx = reader.readInt();
            greenCostOfIdx = reader.readInt();
            blueCostOfIdx = reader.readInt();
            costOfLastRed[idx] = Math.min(costOfLastGreen[beforeIdx] + redCostOfIdx, costOfLastBlue[beforeIdx] + redCostOfIdx);
            costOfLastGreen[idx] = Math.min(costOfLastBlue[beforeIdx] + greenCostOfIdx, costOfLastRed[beforeIdx] + greenCostOfIdx);
            costOfLastBlue[idx] = Math.min(costOfLastRed[beforeIdx] + blueCostOfIdx, costOfLastGreen[beforeIdx] + blueCostOfIdx);
        }

        totalCost = Math.min(costOfLastRed[N], costOfLastGreen[N]);
        totalCost = Math.min(totalCost, costOfLastBlue[N]);
    }

    static class Reader {
        static BufferedReader bufferedReader;
        static StringTokenizer stringTokenizer;
        
        Reader() {
            bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        }
        
        String read() {
            while (stringTokenizer == null || !stringTokenizer.hasMoreElements()) {
                try {
                    stringTokenizer = new StringTokenizer(bufferedReader.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return stringTokenizer.nextToken();
        }

        int readInt() {
            return Integer.parseInt(read());
        }
    }
}

부족한 점이나 피드백은 사랑입니다 :)