Problem
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.
Constraints:
1 <= nums.length <= 10^5-10^9 <= nums[i] <= 10^9
Solution (Java)
class Solution {
public long zeroFilledSubarray(int[] nums) {
long cnt = 0L;
long local = 0L;
for (int n : nums) {
if (n == 0) {
cnt += ++local;
} else {
local = 0;
}
}
return cnt;
}
}
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).