Question

How to merge overlapping ranges (start,end),(start,end) in Java

Answer 1

import java.util.Comparator;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MergeRanges {

    public static List<int[]> mergeRanges(List<int[]> ranges) {
        // Sort by start value
        ranges.sort(Comparator.comparingInt(a -> a[0]));

        List<int[]> merged = new ArrayList<>();

        for (int[] r : ranges) {
            int start = r[0];
            int end   = r[1];

            if (merged.isEmpty() || start > merged.get(merged.size() - 1)[1]) {
                merged.add(new int[]{start, end});
            } else {
                int[] last = merged.get(merged.size() - 1);
                last[1] = Math.max(last[1], end);
            }
        }

        return merged;
    }

    public static void main(String[] args) {
        List<int[]> ranges = Arrays.asList(
            new int[]{302, 447},
            new int[]{488, 489},
            new int[]{121, 234},
            new int[]{200, 421},
            new int[]{140, 354}
        );

        List<int[]> result = mergeRanges(ranges);

        for (int[] r : result) {
            System.out.println("(" + r[0] + ", " + r[1] + ")");
        }
    }
}


/*
run:

(121, 447)
(488, 489)

*/

 

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