leetcode 1893. Check if All the Integers in a Range Are Covered（python）

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描述

You are given a 2D integer array ranges and two integers left and right. Each ranges[i] = [start_i, end_i] represents an inclusive interval between start_i and end_i.

Return true if each integer in the inclusive range [left, right] is covered by at least one interval in ranges. Return false otherwise.

An integer x is covered by an interval ranges[i] = [start_i, end_i] if start_i <= x <= end_i.

Example 1:

Input: ranges = [[1,2],[3,4],[5,6]], left = 2, right = 5
Output: true
Explanation: Every integer between 2 and 5 is covered:
- 2 is covered by the first range.
- 3 and 4 are covered by the second range.
- 5 is covered by the third range.

Example 2:

Input: ranges = [[1,10],[10,20]], left = 21, right = 21
Output: false
Explanation: 21 is not covered by any range.

Note:

1 <= ranges.length <= 50

1 <= start_i <= end_i <= 50

1 <= left <= right <= 50

解析

根据题意，就是给出一个列表 ranges ，里面都是一个个范围，判断 [left, right] 中的每个数字至少都被一个 range 所包含，如果 [left, right] 中的每个数字都至少被一个范围覆盖直接返回 True ， 否则返回 False 。思路简单，直接看代码 。

解答

class Solution(object):
    def isCovered(self, ranges, left, right):
        """
        :type ranges: List[List[int]]
        :type left: int
        :type right: int
        :rtype: bool
        """
        for i in range(left, right + 1):
            count = 0
            for r in ranges:
                count += 1
                if r[0] <= i <= r[1]:
                    break
                elif count==len(ranges):
                    return False
        return True
            	      
		

运行结果

Runtime: 28 ms, faster than 75.57% of Python online submissions for Check if All the Integers in a Range Are Covered.
Memory Usage: 13.2 MB, less than 89.31% of Python online submissions for Check if All the Integers in a Range Are Covered.

解析

另外可以将 ranges 表示的范围中的数字都放入一个集合 a 中，将 [left,right] 中的数字放入一个集合 b 中，然后求两个集合中间的交集是否等于 b ，如果等于直接返回 True ，否则返回 False 。

解答

class Solution(object):
    def isCovered(self, ranges, left, right):
        """
        :type ranges: List[List[int]]
        :type left: int
        :type right: int
        :rtype: bool
        """
        a = set(x for x,y in ranges for x in range(x,y+1))
        b = set(x for x in range(left, right+1))
        return a.intersection(b)==b

            	      
		

运行结果

Runtime: 28 ms, faster than 58.93% of Python online submissions for Check if All the Integers in a Range Are Covered.
Memory Usage: 13.7 MB, less than 7.74% of Python online submissions for Check if All the Integers in a Range Are Covered.

原题链接：leetcode.com/problems/ch…

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