From 2a8e5bb69def5e142afd6e9a952656c1187a6ec6 Mon Sep 17 00:00:00 2001
From: "Kai.Yuan" <kent.yuan@Gmail.com>
Date: Wed, 10 Apr 2024 21:59:56 +0200
Subject: [PATCH] [fix-merging-overlapping] fix

---
 .../MergeOverlappingIntervals.java            | 18 +++++------
 .../MergeIntervalsUnitTest.java               | 32 ++++++++++++-------
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/MergeOverlappingIntervals.java b/algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/MergeOverlappingIntervals.java
index ba424772d5..ec7081bec7 100644
--- a/algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/MergeOverlappingIntervals.java
+++ b/algorithms-modules/algorithms-miscellaneous-8/src/main/java/com/baeldung/algorithms/mergeintervals/MergeOverlappingIntervals.java
@@ -1,23 +1,22 @@
 package com.baeldung.algorithms.mergeintervals;
 
+import static java.lang.Integer.max;
+
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.List;
 
 public class MergeOverlappingIntervals {
 
     public List<Interval> doMerge(List<Interval> intervals) {
-        // Sort the intervals based on start time
-        intervals.sort((one, two) -> one.start - two.start);
-
-        // Create somewhere to put the merged list, start it off with the earliest starting interval
+        intervals.sort(Comparator.comparingInt(interval -> interval.start));
         ArrayList<Interval> merged = new ArrayList<>();
         merged.add(intervals.get(0));
 
-        // Loop over each interval and merge if start time is before the end time of the
-        // previous interval
         intervals.forEach(interval -> {
-            if (merged.get(merged.size() - 1).end > interval.start) {
-                merged.get(merged.size() - 1).setEnd(interval.end);
+            Interval lastMerged = merged.get(merged.size() - 1);
+            if (interval.start <= lastMerged.end){
+                lastMerged.setEnd(max(interval.end, lastMerged.end));
             } else {
                 merged.add(interval);
             }
@@ -25,5 +24,4 @@ public class MergeOverlappingIntervals {
 
         return merged;
     }
-
-}
+}
\ No newline at end of file
diff --git a/algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/mergeintervals/MergeIntervalsUnitTest.java b/algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/mergeintervals/MergeIntervalsUnitTest.java
index 5f15fe00f6..2d8a94dca4 100644
--- a/algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/mergeintervals/MergeIntervalsUnitTest.java
+++ b/algorithms-modules/algorithms-miscellaneous-8/src/test/java/com/baeldung/algorithms/mergeintervals/MergeIntervalsUnitTest.java
@@ -1,30 +1,38 @@
 package com.baeldung.algorithms.mergeintervals;
 
-import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 
 import org.junit.jupiter.api.Test;
 
 class MergeIntervalsUnitTest {
 
-    private ArrayList<Interval> intervals = new ArrayList<>(Arrays.asList(
-      new Interval(2, 5),
-      new Interval(13, 20),
-      new Interval(11, 15),
-      new Interval(1, 3)
+    private List<Interval> intervals = new ArrayList<>(Arrays.asList(
+        // @formatter:off
+        new Interval(3, 5),
+        new Interval(13, 20),
+        new Interval(11, 15),
+        new Interval(15, 16),
+        new Interval(1, 3),
+        new Interval(4, 5),
+        new Interval(16, 17)
+        // @formatter:on
     ));
-    private ArrayList<Interval> intervalsMerged = new ArrayList<>(Arrays.asList(
-      new Interval(1, 5),
-      new Interval(11, 20)
+    private List<Interval> intervalsMerged = new ArrayList<>(Arrays.asList(
+        // @formatter:off
+        new Interval(1, 5),
+        new Interval(11, 20)
+        // @formatter:on
     ));
 
     @Test
     void givenIntervals_whenMerging_thenReturnMergedIntervals() {
         MergeOverlappingIntervals merger = new MergeOverlappingIntervals();
-        ArrayList<Interval> result = (ArrayList<Interval>) merger.doMerge(intervals);
-        assertArrayEquals(intervalsMerged.toArray(), result.toArray());
+        List<Interval> result = merger.doMerge(intervals);
+        assertEquals(intervalsMerged, result);
     }
 
-}
+}
\ No newline at end of file