LC-3356 Medium LeetCode

3356. Zero Array Transformation II

Read the full problem statement on LeetCode.

Difficulty: medium Acceptance: 44% Topics: Array, Binary Search, Prefix Sum

Reading material

Arrays & Hashing 12 min Binary Search 12 min Prefix Sums & Difference Arrays 11 min

Reference solution (spoiler · python)

# Time:  O((n + q) * logn)
# Space: O(n)

# binary search, line sweep
class Solution(object):
    def minZeroArray(self, nums, queries):
        """
        :type nums: List[int]
        :type queries: List[List[int]]
        :rtype: int
        """
        def binary_search(left, right, check):
            while left <= right:
                mid = left+(right-left)//2
                if check(mid):
                    right = mid-1
                else:
                    left = mid+1
            return left

        def check(k):
            events = [0]*(len(nums)+1)
            for i in xrange(k):
                events[queries[i][0]] += queries[i][2]
                events[queries[i][1]+1] -= queries[i][2]
            curr = 0
            for i in xrange(len(nums)):
                curr += events[i]
                if nums[i] > curr:
                    return False
            return True
        
        result = binary_search(0, len(queries), check)
        return result if result <= len(queries) else -1

Solution from kamyu104/LeetCode-Solutions · MIT