leetcode986. Interval List Intersections

Posted 2021-02-07 seyjs

题目如下：

Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order.

Return the intersection of these two interval lists.

(Formally, a closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b.  The intersection of two closed intervals is a set of real numbers that is either empty, or can be represented as a closed interval.  For example, the intersection of [1, 3] and [2, 4] is [2, 3].)

 

Example 1:

Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]]
Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
Reminder: The inputs and the desired output are lists of Interval objects, and not arrays or lists.

解题思路：因为A与B的最大长度是1000，因此O(n^2)的时间复杂度是可以接受的。依次比较A与B中的所有元素，求出交集即可。

代码如下：

# Definition for an interval.
class Interval(object):
    def __init__(self, s=0, e=0):
        self.start = s
        self.end = e

class Solution(object):
    def intervalIntersection(self, A, B):
        """
        :type A: List[Interval]
        :type B: List[Interval]
        :rtype: List[Interval]
        """
        res = []
        for a in A:
            for b in B:
                if a.end < b.start:
                    break
                elif a.start > b.end:
                    continue
                else:
                    res.append(Interval(max(a.start,b.start),min(a.end,b.end)))
        return res