add: IdentifyAllIntervalOverlaps

Author: Jer3myYu

java/Intervals/IdentifyAllIntervalOverlaps.java

@@ -0,0 +1,48 @@
+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 IdentifyAllIntervalOverlaps {
+    public List<Interval> identifyAllIntervalOverlaps(List<Interval> intervals1, List<Interval> intervals2) {
+        List<Interval> overlaps = new ArrayList<>();
+        int i, j;
+        i = j = 0;
+        while (i < intervals1.size() && j < intervals2.size()) {
+            // Set A to the interval that starts first and B to the other 
+            // interval.
+            Interval A, B;
+            if (intervals1.get(i).start <= intervals2.get(j).start) {
+                A = intervals1.get(i);
+                B = intervals2.get(j);
+            } else {
+                A = intervals2.get(j);
+                B = intervals1.get(i);
+            }
+            // If there's an overlap, add the overlap.
+            if (A.end >= B.start) {
+                overlaps.add(new Interval(B.start, Math.min(A.end, B.end)));
+            }
+            // Advance the pointer associated with the interval that ends 
+            // first.
+            if (intervals1.get(i).end < intervals2.get(j).end) {
+                i++;
+            } else {
+                j++;
+            }
+        }
+        return overlaps;
+    }
+}