This useful data structure confusingly goes by several different names. Binary indexed tree: https://community.topcoder.com/tc?module=Static&d1=tutorials&d2=bi

This useful data structure confusingly goes by several different names. Binary indexed tree: https://community.topcoder.com/tc?module=Static&d1=tutorials&d2=binaryIndexedTrees https://community.topcoder.com/tc?module=Static&d1=tutor... Cumulative frequency table (which interestingly enough Simon Tatham claims to have independently invented): http://www.chiark.greenend.org.uk/~sgtatham/algorithms/cumulative.html http://www.chiark.greenend.org.uk/~sgtatham/algorithms/cumul...