Leetcode - subarray-sum-equals-k
https://leetcode.com/problems/subarray-sum-equals-k/
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].
The question is easier for just counting the total number of subarrays. It's a bit like 2 sum. Iterate the array and then sum every item and store in a map. The key of map is current sum and the value is number. Once key sum - k is in the map, then there's a result for the sum equals to k.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | func subarraySum(nums []int, k int) int { result := 0 sum := 0 preSum := map[int]int{ 0: 1, } for i := 0; i < len(nums); i++{ sum += nums[i] if val, ok := preSum[sum-k]; ok { result += val } preSum[sum]++ } return result} |
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