This is a classic problem in Amazon back-to-back interviews. This article demonstrates the application of Prefix Sum and Sliding Window techniques using the "Subarray Sum Equals Target" problem. oavoservice helps you quickly master core techniques.
📋 Problem Description
Given an array of integers and a target sum, find a continuous subarray that sums up to the target value.
Example:
Input: nums = [1, 2, 3, 7, 5], target = 12
Output: [2, 4] (Subarray [3, 7, 5])
🎯 Core Concepts
- Prefix Sum - Quickly calculate range sum
- Hash Map - O(n) time complexity
- Sliding Window - Optimization for positive number arrays
- Edge Case Handling - Multiple solutions
💡 Solution Strategy (oavoservice Guidance)
Method 1: Prefix Sum + Hash Map
def subarraySum(nums, target):
prefix_sum = 0
sum_map = {0: -1} # {prefix_sum: index}
for i, num in enumerate(nums):
prefix_sum += num
if prefix_sum - target in sum_map:
start = sum_map[prefix_sum - target] + 1
return [start, i]
sum_map[prefix_sum] = i
return []
Time Complexity: O(n) Space Complexity: O(n)
Method 2: Sliding Window (Only for Positive Numbers)
def subarraySum_positive(nums, target):
left = 0
current_sum = 0
for right in range(len(nums)):
current_sum += nums[right]
while current_sum > target and left <= right:
current_sum -= nums[left]
left += 1
if current_sum == target:
return [left, right]
return []
💼 How oavoservice Helps
Algorithm Selection - Choose the best algorithm based on data characteristics. Code Implementation - Clear logic and comments. Optimization Discussion - Optimization strategies for different scenarios.
Contact oavoservice for professional VO interview assistance!
Tags: #Amazon #PrefixSum #SlidingWindow #Subarray #VOHelp #InterviewPrep #1point3acres
Need real interview questions? Contact WeChat Coding0201 immediately to get real questions.