题目
Given an array of positive integers nums
and a positive integer target
, return the minimal length of a contiguous subarray [numsl, numsl+1, ..., numsr-1, numsr]
of which the sum is greater than or equal to target
. If there is no such subarray, return 0
instead.
Example 1:
Input: target = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: The subarray [4,3] has the minimal length under the problem constraint.
Example 2:
Input: target = 4, nums = [1,4,4]
Output: 1
Example 3:
Input: target = 11, nums = [1,1,1,1,1,1,1,1]
Output: 0
Constraints:
1 <= target <= 109
1 <= nums.length <= 105
1 <= nums[i] <= 105
Follow up: If you have figured out the O(n)
solution, try coding another solution of which the time complexity is O(n log(n))
.
思路
滑动窗口,当窗口内数字和大于等于target时,滑动左窗口至数字和小于target,将此时窗口大小记录下来,等到循环结束,所有窗口大小的最小值就是结果。
代码
python版本:
class Solution:
def minSubArrayLen(self, target: int, nums: List[int]) -> int:
cnt = 0
minl = math.inf
l = 0
for r in range(len(nums)):
cnt += nums[r]
if cnt >= target:
while cnt >= target and l <= r:
cnt -= nums[l]
l += 1
minl = min(minl, r-l+2)
return 0 if minl == math.inf else minl