add: MergeOverlappingIntervals

Author: Jer3myYu

java/Intervals/MergeOverlappingIntervals.java

@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import DS.Interval;
+
+/*
+    // Definition of Interval:
+    class Interval {
+        public int start;
+        public int end;
+        public Interval(int start, int end) {
+            this.start = start;
+            this.end = end;
+        }
+    }
+ */
+
+public class MergeOverlappingIntervals {
+    public List<Interval> mergeOverlappingIntervals(List<Interval> intervals) {
+        Collections.sort(intervals, (a, b) -> Integer.compare(a.start, b.start));
+        List<Interval> merged = new ArrayList<>();
+        merged.add(intervals.get(0));
+        for (int i = 1; i < intervals.size(); i++) {
+            Interval B = intervals.get(i);
+            Interval A = merged.get(merged.size() - 1);
+            // If A and B don't overlap, add B to the merged list.
+            if (A.end < B.start) {
+                merged.add(B);
+            }
+            // If they do overlap, merge A with B.
+            else {
+                A.end =  Math.max(A.end, B.end);
+            }
+        }
+        return merged;
+    }   
+}