# MeetingRoom

Given an array of meeting time intervals consisting of start and end times \[\[s1,e1],\[s2,e2],...] (si < ei), determine if a person could attend all meetings.

> Example 1:\
> Input : \[\[0,30]\[5,10],\[15,20]]\
> Output : false
>
> Example 2 :\
> Input : \[\[7,10],\[2,4]]\
> Output : true

**Solution**\
1\. 시작 시간 기준으로 **Sorting**.\
2\. 이전의 끝 > 다음의 시작 **Compare**.

**의사코드->Java 언어로 구현**

```java
//Interval 클래스 구현
class Interval {
    int start;
    int end;
    //constructor(생성자)로 초기화
    Interval() {
        this.start = 0;
        this.end = 0;
    }
    Interval(int s, int e) {
        this.start = s;
        this.end = e;
    }
}
//Solution 시작
public class MeetingRoom {
    public static void main(String[] args) {
        MeetingRoom a = new MeetingRoom();
        Interval in1 = new Interval(0,30);
        Interval in2 = new Interval(10,15);
        Interval in3 = new Interval(20,25);
        
        Interval[] intervals = {in1,in2,in3};
        System.out.println(a.solve(intervals));
    }
    public boolean solve(Interval[] intervals) {
        if(intervals == null)
            return false;
        print(Intervals);
        //1.시작 시간 기준으로 Sorting.
        Arrays.sort(intervals, Comp);
        //2.이전의 끝 > 다음의 시작 Compare.
        for(int i=1; i<intervals.length;i++) {
            if(intervals[i-1].end > intervals[i].start)
                return false;
        }
        return true;
    }
    Comparator<Interval> Comp = new Comparator<Interval>(){
        @Override
        public int compare(Interval o1, Interval o2) {
            return o1.start - o2.start;
        }
    };
    public void print(Interval[] intervals) {
        for(int i = 0; i<intervals.length; i++) {
            Interval in = intervals[i];
            System.out.println(in.start + "  " + in.end);
        }
        
    }
}
```

**Java 복습**

Compartor와 Comparable\
\- Comparable : 기본 정렬기준을 구현하는 데 사용\
\- **Comparator** : 기본 정렬기준 외에 다른 기준으로 정렬하고자 할 때 사용

* 오름차순 정렬\
  1\. Comparator 오버라이드

```java
Comparator<Interval> Comp = new Comparator<Interval>(){
    @Override
    public int compare(Interval o1, Interval o2) {
        return o1.start - o2.start;
    }
};
```

2\. Comparator 안에서 움직이는 것은 compareTo 메소드이다.

```java
//compareTo 작동원리 이해.오른쪽이 크면 -1
public void compareToTest() {
    Integer num = 5;
    System.out.println(num.compareTo(3));//1
    System.out.println(num.compareTo(5));//0
    System.out.println(num.compareTo(88));//-1
}
```

3\. 람다식을 이용한 오름차순 정렬.&#x20;

**Arrays.sort(array, 람다식)**\
람다식 : **(o1,o2)->o1.start-o2.start**

```java
Arrays.sort(intervals,(o1,o2)->o1.start-o2.start);
```


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