package top100liked

import "testing"

// https://leetcode.cn/problems/subarray-sum-equals-k/description/?envType=study-plan-v2&envId=top-100-liked
// 这题好难，理解不能

func subarraySum(nums []int, k int) int {
	freq := make(map[int]int)
	freq[0] = 1
	cur := 0
	res := 0
	for _, v := range nums {
		cur += v
		if f, ok := freq[cur-k]; ok {
			res += f
		}
		freq[cur]++
	}
	return res
}

func TestS10(t *testing.T) {
	println(subarraySum([]int{1, 1, 1}, 2))
	println(subarraySum([]int{1, 2, 3}, 3))
	println(subarraySum([]int{1}, 0))
	println(subarraySum([]int{-1, -1, 1}, 0))
}