README.md

757. Set Intersection Size At Least Two

You are given a 2D integer array intervals where intervals[i] = [starti, endi] represents all the integers from starti to endi inclusively.

A containing set is an array nums where each interval from intervals has at least two integers in nums.

• For example, if intervals = [[1,3], [3,7], [8,9]], then [1,2,4,7,8,9] and [2,3,4,8,9] are containing sets.

Return the minimum possible size of a containing set.

Example 1:

Input: intervals = [[1,3],[3,7],[8,9]]
Output: 5
Explanation: let nums = [2, 3, 4, 8, 9].
It can be shown that there cannot be any containing array of size 4.

Example 2:

Input: intervals = [[1,3],[1,4],[2,5],[3,5]]
Output: 3
Explanation: let nums = [2, 3, 4].
It can be shown that there cannot be any containing array of size 2.

Example 3:

Input: intervals = [[1,2],[2,3],[2,4],[4,5]]
Output: 5
Explanation: let nums = [1, 2, 3, 4, 5].
It can be shown that there cannot be any containing array of size 4.

Constraints:

• 1 <= intervals.length <= 3000
• intervals[i].length == 2
• 0 <= starti < endi <= 108

Solutions (Python)

1. Solution

class Solution:
    def intersectionSizeTwo(self, intervals: List[List[int]]) -> int:
        intervals.sort(key=lambda interval: (interval[1], interval[0]))
        nums = [intervals[0][1] - 1, intervals[0][1]]

        for start, end in intervals[1:]:
            if start <= nums[-2]:
                continue
            elif start > nums[-1]:
                nums.append(end - 1)
                nums.append(end)
            elif end > nums[-1]:
                nums.append(end)
            else:
                nums.pop()
                nums.append(end - 1)
                nums.append(end)

        return len(nums)