560. Subarray Sum Equals K
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Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k.
A subarray is a contiguous non-empty sequence of elements within an array.
Example 1:
Input: nums = [1,1,1], k = 2 Output: 2
Example 2:
Input: nums = [1,2,3], k = 3 Output: 2
Constraints:
1 <= nums.length <= 2 * 104-1000 <= nums[i] <= 1000-107 <= k <= 107
Hints
Hint 1
Will Brute force work here? Try to optimize it.
Hint 2
Can we optimize it by using some extra space?
Hint 3
What about storing sum frequencies in a hash table? Will it be useful?
Hint 4
sum(i,j)=sum(0,j)-sum(0,i), where sum(i,j) represents the sum of all the elements from index i to j-1.
Can we use this property to optimize it.