subarray-sum-equals-k

Subarray Sum Equals K

LeetCode #: 560

Difficulty: Medium

Topic: Array, Hash Table.

Problem

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.

Example 1:

Input:nums = [1,1,1], k = 2
Output: 2

Note:

• The length of the array is in range [1, 20,000].
• The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].

Complexity Analysis

Time complexity: O(n). We loop through the array only once.

Space complexity: O(n). Hash map can contain up to n entries.