Insert Interval

Author: applewjg

InsertInterval.java

@@ -0,0 +1,86 @@
+/*
+ Author:     King, wangjingui@outlook.com
+ Date:       Dec 14, 2014
+ Problem:    Insert Interval
+ Difficulty: Medium
+ Source:     https://oj.leetcode.com/problems/insert-interval/
+ Notes:
+ 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].
+
+ Solution: For example 2:
+           1. compare [1,2] with [4,9], then insert [1,2];
+           2. merge [3,5] with [4,9], get newInterval = [3,9];
+           3. merge [6,7] with [3,9], get newInterval = [3,9];
+           4. merge [8,10] with [3,9], get newInterval = [3,10];
+           5. compare [12,16] with [3,10], insert newInterval [3,10], then all the remaining intervals...
+           Solution 1 : Time O(N).
+           Solution 2 : Time O(Log(N)).
+*/
+
+/**
+ * Definition for an interval.
+ * public class Interval {
+ *     int start;
+ *     int end;
+ *     Interval() { start = 0; end = 0; }
+ *     Interval(int s, int e) { start = s; end = e; }
+ * }
+ */
+public class Solution {
+    public List<Interval> insert_1(List<Interval> intervals, Interval newInterval) {
+        List<Interval> res = new ArrayList<Interval>();
+        boolean inserted = false;
+        for (Interval it : intervals) {
+            if (inserted || it.end < newInterval.start) {
+                res.add(it);
+            } else if (it.start > newInterval.end) {
+                res.add(newInterval);
+                res.add(it);
+                inserted = true;
+            } else {
+                newInterval.start = Math.min(newInterval.start, it.start);
+                newInterval.end = Math.max(newInterval.end, it.end);
+            }
+        }
+        if (inserted == false) res.add(newInterval);
+        return res;
+    }
+    public List<Interval> insert(List<Interval> intervals, Interval newInterval) {
+        List<Interval> res = new ArrayList<Interval>();
+        int n = intervals.size();
+        int left = 0, right = n - 1;
+        while (left <= right) {
+            int mid = left + (right - left) / 2;
+            if (intervals.get(mid).start > newInterval.start) right = mid - 1;
+            else left = mid + 1;
+        }
+        int idxStart = right;
+        left = 0; right = n - 1;
+        while (left <= right) {
+            int mid = left + (right - left) / 2;
+            if (intervals.get(mid).end < newInterval.end) left = mid + 1;
+            else right = mid - 1;
+        }
+        int idxEnd = left;
+        if (idxStart >= 0 && newInterval.start <= intervals.get(idxStart).end) {
+            newInterval.start = intervals.get(idxStart--).start;
+        }
+        if (idxEnd < n && newInterval.end >= intervals.get(idxEnd).start) {
+            newInterval.end = intervals.get(idxEnd++).end;
+        }
+        for (int i = 0; i <= idxStart; ++i) {
+            res.add(intervals.get(i));
+        }
+        res.add(newInterval);
+        for (int i = idxEnd; i < n; ++i) {
+            res.add(intervals.get(i));
+        }
+        return res;
+    }
+}