Grokking the Coding Interview: Patterns for Coding Questions
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Maximum Size Subarray Sum Equals k (medium)

Problem Statement

Given an array of integers nums and an integer k, find the length of the longest subarray that sums to k. If no such subarray exists, return 0.

Examples

Example 1:

  • Input: nums = [1, 2, 3, -2, 5], k = 5
  • Output: 2
  • Explanation: The longest subarray with a sum of 5 is [2, 3], which has a length of 2.

Example 2:

  • Input: nums = [-2, -1, 2, 1], k = 1
  • Output: 2
  • Explanation: The longest subarray with a sum of 1 is [-1, 2], which has a length of 2.

Example 3:

  • Input:

.....

.....

.....

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Mohammed Dh Abbas

Mohammed Dh Abbas

· 2 years ago

class Solution:
    def maxSubArrayLen(self, nums, k):
        
        sum_lookup = {}
        acc_sum = 0 # accumulated sum
        length = 0 
        
        for index, num in enumerate(nums):
            acc_sum += num 
            sum_lookup[acc_sum] = index
        
            # if the sub array starts from the first location in nums array we use the length up to that point
            # example [1, -1, 0, 2, 3], K = 2 answer is 4 
            if acc_sum == k:
                length = index + 1
            
            # search "O(1) using hashmap" for any accumulated sum that is = acc_sum - k then measure the difference of indexes length
            # example [3, 4, 7, 2, -3, 1, 4, 2], k = 7 answer is 4
            elif acc_sum - k in sum_lookup:
                len