What is the primary pattern for solving the Running Sum of 1D Array problem?

The primary pattern is the 'Prefix Sum' pattern, where each element in the result array is the cumulative sum up to that index.

Can I solve this problem without extra space?

Yes, you can solve this problem in-place by updating the original array, avoiding the need for additional memory allocation.

What is the time complexity of this problem?

The time complexity is O(n), where n is the length of the input array, since each element is processed once.

How does GhostInterview assist in solving this problem?

GhostInterview provides step-by-step guidance and ensures you apply the correct algorithmic approach while avoiding common pitfalls like unnecessary space usage.

What should I do if I encounter negative numbers in the array?

The approach remains the same, as the cumulative sum will handle negative values correctly, just like positive values.

#1480

Easy

auto_awesome前缀和

LeetCode 题解工作台

一维数组的动态和

给你一个数组 nums 。数组「动态和」的计算公式为： runningSum[i] = sum(nums[0]…nums[i]) 。请返回 nums 的动态和。示例 1：输入： nums = [1,2,3,4] 输出： [1,3,6,10] 解释：动态和计算过程为 [1, 1+…

数组前缀和

题目描述

给你一个数组 nums 。数组「动态和」的计算公式为：runningSum[i] = sum(nums[0]…nums[i]) 。

请返回 nums 的动态和。

示例 1：

输入：nums = [1,2,3,4]
输出：[1,3,6,10]
解释：动态和计算过程为 [1, 1+2, 1+2+3, 1+2+3+4] 。

示例 2：

输入：nums = [1,1,1,1,1]
输出：[1,2,3,4,5]
解释：动态和计算过程为 [1, 1+1, 1+1+1, 1+1+1+1, 1+1+1+1+1] 。

示例 3：

输入：nums = [3,1,2,10,1]
输出：[3,4,6,16,17]

提示：

1 <= nums.length <= 1000
-10^6 <= nums[i] <= 10^6

lightbulb

解题思路

方法一：前缀和

我们直接遍历数组，对于当前元素 $nums[i]$ ，我们将其与前缀和 $nums[i-1]$ 相加，即可得到当前元素的前缀和 $nums[i]$ 。

时间复杂度 $O(n)$ ，其中 $n$ 为数组长度。空间复杂度 $O(1)$ 。

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class Solution:
    def runningSum(self, nums: List[int]) -> List[int]:
        return list(accumulate(nums))

speed

复杂度分析

指标	值
时间	Depends on the final approach
空间	Depends on the final approach

psychology

面试官常问的追问

外企场景

question_mark
Ability to optimize space usage by modifying the array in-place.
question_mark
Understanding of the prefix sum pattern and its efficiency in cumulative calculations.
question_mark
Efficiency in both time and space while solving the problem, especially with the potential large input size.

warning

常见陷阱

外企场景

error
Failing to update the array in-place or unnecessarily using extra space.
error
Overcomplicating the solution by introducing unnecessary intermediate steps.
error
Misunderstanding the prompt, leading to incorrect implementation of the cumulative sum.

swap_horiz

进阶变体

外企场景

arrow_right_alt
Implement the solution using a recursive approach.
arrow_right_alt
Handle cases where the array might contain negative numbers.
arrow_right_alt
Return the prefix sum of a subarray rather than the entire array.

help

常见问题

外企场景

继续练习

#1508 子数组和排序后的区间和 #1444 切披萨的方案数 #1442 形成两个异或相等数组的三元组数目