Subarray Sum Equals K

LeetCode: https://leetcode.com/problems/subarray-sum-equals-k/

Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals k.

1def subarraySum(nums: List[int], k: int) -> int:
2    count = {0: 1}
3    pref = 0
4    res = 0
5    
6    for x in nums:
7        pref += x
8        need = pref - k
9        res += count.get(need, 0)
10        count[pref] = count.get(pref, 0) + 1
11    
12    return res

Range Sum Query - Immutable

Find Pivot Index

k=3

pref=0

res=0

count={ 0 }

Step 1 / 7

Step 1:

Initialize count map with count[0]=1 (empty prefix). pref=0, res=0.

Pointers: i=-1

Focus: default

k=3pref=0res=0