leetcode 2348. Number of Zero-Filled Subarrays（python）

描述

Given an integer array nums, return the number of subarrays filled with 0.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

Input: nums = [1,3,0,0,2,0,0,4]
Output: 6
Explanation: 
There are 4 occurrences of [0] as a subarray.
There are 2 occurrences of [0,0] as a subarray.
There is no occurrence of a subarray with a size more than 2 filled with 0. Therefore, we return 6

Example 2:

Input: nums = [0,0,0,2,0,0]
Output: 9
Explanation:
There are 5 occurrences of [0] as a subarray.
There are 3 occurrences of [0,0] as a subarray.
There is 1 occurrence of [0,0,0] as a subarray.
There is no occurrence of a subarray with a size more than 3 filled with 0. Therefore, we return 9.

Example 3:

Input: nums = [2,10,2019]
Output: 0
Explanation: There is no subarray filled with 0. Therefore, we return 0.

Note:

1 <= nums.length <= 10^5
-10^9 <= nums[i] <= 10^9

解析

根据题意，给定一个整数数组 nums ，返回用 0 填充的所有子数组的数量。子数组是数组中元素的连续非空序列。

这道题其实也不难，只需要从左到右遍历 nums 中的元素，如果元素不为 0 ，则 t 一直设置为 0 ，如果出现元素为 0 则用 t 不断累积可能出现的全 0 的子数组的个数并将其加入到 result 中，不断继续后面的遍历操作直到结束。

时间复杂度为 O(N) ，空间复杂度为 O(1)。

解答

class Solution(object):
    def zeroFilledSubarray(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        result = 0
        t = 0
        for c in nums:
            if c:
                t = 0
            else:
                t+= 1
                result += t
        return result

运行结果

48 / 48 test cases passed.
Status: Accepted
Runtime: 1340 ms
Memory Usage: 23.1 MB

原题链接

https://leetcode.com/contest/biweekly-contest-83/problems/number-of-zero-filled-subarrays/

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