Question

How to detect whether any intervals overlap in an array of start and end times with Java

Answer 1

import java.util.Arrays;

public class Main {

    static boolean hasOverlap(int[][] intervals) {
        if (intervals.length == 0) {
            return true;
        }

        // Sorting is essential because once intervals are ordered by 
        // start time, any overlap can only occur between adjacent intervals.
        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
        // (5,9), (11,12), (15,17)

        // (5,9) and (11,12) → 11 < 9? No
        // (11,12) and (15,17) → 15 < 12? No

        // The loop compares each interval with the one before it.
        for (int i = 1; i < intervals.length; i++) {
            if (intervals[i][0] < intervals[i - 1][1]) {

                return false; // Overlap found
            }
        }

        return true; // No overlap
    }

    public static void main(String[] args) {
        int[][] intervals = {
            {11, 12}, {5, 9}, {15, 17}
        };

        if (hasOverlap(intervals))
            System.out.println("There are NO overlapping intervals");
        else
            System.out.println("There ARE overlapping intervals");
    }
}


/*
run:

There are NO overlapping intervals

*/

 

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