方法一、暴力法
方法二、前缀和 + HashMap
求解和的方式往往能够分解成sum-k方式，查找此key是否在该dict中，count累加计数
# prefix sum
nums = [1,1,1,1]
k, count = 2, 0
dic = {0:1} # 和为key的前缀和有value个
prefix_sum = 0
for i in range(len(nums)):
prefix_sum += nums[i]
if prefix_sum - k in dic:
count += dic[prefix_sum-k]
if prefix_sum in dic:
dic[prefix_sum] += 1
else:
dic[prefix_sum] = 1
count
标签：count,key,nums,sum,dic,prefix,连续,数组 From： https://www.cnblogs.com/demo-deng/p/16615128.html