problem560

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560. Subarray Sum Equals K (Medium)

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

 

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

Related Topics

[Array] [Hash Table] [Prefix Sum]

Similar Questions

1. Two Sum (Easy)
2. Continuous Subarray Sum (Medium)
3. Subarray Product Less Than K (Medium)
4. Find Pivot Index (Easy)
5. Subarray Sums Divisible by K (Medium)
6. Minimum Operations to Reduce X to Zero (Medium)

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.