Minimum Value to Get Positive Step by Step Sum — LeetCode 1413 Python Solution

The problem

Given an array of integers nums, you start with an initial positive value startValue. In each iteration, you calculate the step by step sum of startValue plus elements in nums (from left to right).

Example

Input

nums = [-3,2,-3,4,2]

Output

5

Explanation

If you choose startValue = 4, in the third iteration your step by step sum is less than 1.

Python solution

class Solution:
    def minStartValue(self, nums: List[int]) -> int:
        s, t = 0, inf
        for num in nums:
            s += num
            t = min(t, s)
        return max(1, 1 - t)

Complexity

Pattern: Prefix Sum

Precompute running totals once so any range query becomes a single subtraction. LeetCode 1413. Minimum Value to Get Positive Step by Step Sum is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Prefix Sum.

The prefix sum guide has the Python template for the pattern and the 157 LeetCode problems that use it.

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