##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######
##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######
Prefix sum + deque
Given an integer array and an integer , find the length of the shortest non-empty subarray with sum at least . Return if no such subarray exists.
This problem combines prefix sums with monotonic deques. It's significantly harder than sliding window maximum. Arrays can contain negative numbers, which is why a simple sliding window doesn't work.
