Insert Interval

Author: mengli

InsertInterval.java

@@ -0,0 +1,56 @@
+/**
+ * Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).
+ * 
+ * You may assume that the intervals were initially sorted according to their start times.
+ *
+ * Example 1:
+ * Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].
+ *
+ * Example 2:
+ * Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].
+ *
+ * This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].
+ */
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+
+public class InsertInterval {
+	public class IntervalCmp implements Comparator<Interval> {
+
+		@Override
+		public int compare(Interval i1, Interval i2) {
+			if (i1.start < i2.start) {
+				return -1;
+			}
+			if (i1.start == i2.start && i1.end <= i2.end) {
+				return -1;
+			}
+			return 1;
+		}
+
+	}
+
+	public ArrayList<Interval> insert(ArrayList<Interval> intervals,
+			Interval newInterval) {
+		intervals.add(newInterval);
+		Interval[] arr = new Interval[intervals.size()];
+		intervals.toArray(arr);
+		Arrays.sort(arr, new IntervalCmp());
+		intervals.clear();
+		int start = arr[0].start;
+		int end = arr[0].end;
+		for (int i = 1; i < arr.length; i++) {
+			if (arr[i].start <= end) {
+				end = Math.max(end, arr[i].end);
+			} else {
+				intervals.add(new Interval(start, end));
+				start = arr[i].start;
+				end = arr[i].end;
+			}
+		}
+		intervals.add(new Interval(start, end));
+		return intervals;
+	}
+}