merge intervals

Author: idf

352 Data Stream as Disjoint Intervals.py

@@ -0,0 +1,62 @@
+"""
+Given a data stream input of non-negative integers a1, a2, ..., an, ..., summarize the numbers seen so far as a list of
+disjoint intervals.
+
+For example, suppose the integers from the data stream are 1, 3, 7, 2, 6, ..., then the summary will be:
+
+[1, 1]
+[1, 1], [3, 3]
+[1, 1], [3, 3], [7, 7]
+[1, 3], [7, 7]
+[1, 3], [6, 7]
+Follow up:
+What if there are lots of merges and the number of disjoint intervals are small compared to the data stream's size?
+"""
+__author__ = 'Daniel'
+
+
+# Definition for an interval.
+class Interval(object):
+    def __init__(self, s=0, e=0):
+        self.start = s
+        self.end = e
+
+
+class SummaryRanges(object):
+    def __init__(self):
+        """
+        BST is the most efficient, while heap is simple to write
+        Initialize your data structure here.
+        """
+        self.itvls = []
+
+    def addNum(self, val):
+        """
+        O(lg n)
+        :type val: int
+        :rtype: void
+        """
+        self.itvls.append(Interval(val, val))
+
+    def getIntervals(self):
+        """
+        O(n lg n)
+        :rtype: List[Interval]
+        """
+        self.itvls.sort(key=lambda x: x.start)
+
+        ret = [self.itvls[0]]
+        for itvl in self.itvls[1:]:
+            pre = ret[-1]
+            if itvl.start <= pre.end + 1:
+                pre.end = max(itvl.end, pre.end)
+            else:
+                ret.append(itvl)
+
+        self.itvls = ret
+        return ret
+
+# Your SummaryRanges object will be instantiated and called as such:
+# obj = SummaryRanges()
+# obj.addNum(val)
+# param_2 = obj.getIntervals()