Problem Source: 252. Meeting Rooms

**1. Understand the problem**

We need to determine whether the user could attend all meetings without any conflict or not.

2 meeting `a`

and `b`

will conflict with each other if there is any overlap between `a`

and `b`

.

Here are 2 valid situation that `a`

and `b`

do not conflict each other:

- a.start >= b.end
- b.start >= a.end (this means that one meeting start after the other ends)

Other situations will resolved in an overlap situation.

**2. Solution**

When dealing with interval problems, we need to sort the meeting times in ascending order of start time followed by the ascending order of end time.

With this, when consider 2 interval `I1`

and `I2`

, if `I2.start`

is less than `I1.end`

, they overlap.

Here is the code:

```
class Solution {
public boolean canAttendMeetings(int[][] intervals) {
/**
If the meetings time overlapped, return no.
*/
if (intervals.length <= 1) {
return true;
}
Arrays.sort(intervals, (a, b) -> a[0] == b[0]? a[1] - b[1]: a[0] - b[0]);
for (int i = 0; i < intervals.length - 1; i++) {
int[] interval1 = intervals[i];
int[] interval2 = intervals[i + 1];
if (interval2[0] < interval1[1]) {
return false;
}
}
return true;
}
}
```

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