Leetcode 3356. Zero Array Transformation II

Given range queries that can decrement each index in their range by up to val independently, find the smallest prefix length k such that for every index the total available decrement from the first k queries covering that index is at least nums[i] (otherwise return -1). Key challenge: efficiently test prefixes — typically solved by binary searching k and using a difference/prefix-sum array (or segment tree) to accumulate query contributions.