[알고리즘] 1828. 냉장고

0. 문제

 

JUNGOL

 

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1. 문제 이해

 

1. 그리디 알고리즘 - Activity-Selection Problem

 

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2. 제출

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

public class JOL1828 {

    static int N;
    static Thing[] arr;
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());

        N = Integer.parseInt(st.nextToken());
        arr = new Thing[N];

        for(int i=0; i<N; i++) {
            st = new StringTokenizer(br.readLine());
            Thing thing = new Thing(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
            arr[i] = thing;
        }

        Arrays.sort(arr);

        int ret = 0;
        int cur = -999;
        for(int i=0; i<N; i++) {
            if(arr[i].start > cur) {
                cur = arr[i].end;
                ret++;
            }
        }

        System.out.println(ret);
        br.close();
    }

    static class Thing implements Comparable<Thing> {
        int start, end;
        Thing(int start, int end) {
            this.start = start;
            this.end = end;
        }

        @Override
        public int compareTo(Thing o) {
            return this.end == o.end ? this.start - o.start : this.end - o.end;
        }
    }

}

• return this.end == o.end ? this.start - o.start : this.end - o.end;
  : end를 기준으로 오름차순으로 정렬했다.
• if(arr[i].start > cur) {
  : 앞선 화학물질들과 곂치는 온도가 없다. 즉, 새로운 냉장고가 필요하다.

 

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