add: LargestOverlapOfIntervals

Author: Jer3myYu

java/Intervals/LargestOverlapOfIntervals.java

@@ -0,0 +1,45 @@
+import java.util.ArrayList;
+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 LargestOverlapOfIntervals {
+    public int largestOverlapOfIntervals(List<Interval> intervals) {
+        List<int[]> points = new ArrayList<>();
+        for (Interval interval : intervals) {
+            points.add(new int[]{interval.start, 'S'});
+            points.add(new int[]{interval.end, 'E'});
+        }
+        // Sort in chronological order. If multiple points occur at the same 
+        // time, ensure end points are prioritized before start points.
+        Collections.sort(points, (a, b) -> {
+            if (a[0] == b[0]) return Integer.compare(a[1], b[1]);
+            else return Integer.compare(a[0], b[0]);
+        });
+        int activeInterval= 0;
+        int maxOverlaps = 0;
+        for (int[] point : points) {
+            int time = point[0];
+            int pointType = point[1];
+            if (pointType == 'S') {
+                activeInterval++;
+            } else {
+                activeInterval--;
+            }
+            maxOverlaps = Math.max(maxOverlaps, activeInterval);
+        }
+        return maxOverlaps;
+    }
+}