quartz/content/tmp_script/prefix_sum.md

title	tags
Prefix Sum	basic

假设我们有一个长度为n的数组arr，前缀和数组prefixSum的定义如下：

prefixSum[0] = arr[0] 
prefixSum[1] = arr[0] + arr[1] 
prefixSum[2] = arr[0] + arr[1] + arr[2] 
... 
prefixSum[i] = arr[0] + arr[1] + ... + arr[i]