A JavaScript implementation of Binary Indexed Tree with fast initialization

Binary Indexed Tree also known as Fenwick tree is a data structure providing efficient methods for calculation and manipulation of the prefix sums of a table of values.

This JavaScript implementation is based on the Top Coder article by boba5551. Most of the terms respect to the author's definition except for

• All indexes in the public API are 0 based

There's another implementation by berlysia. Comparing to that, this one is faster for creation. The constructor accepts a defaultFrequency option, which initializes all frequencies in O(1) time complexity.

$ npm install --save fast-binary-indexed-tree

Refer to the document for details.

var BinaryIndexedTree = require('fast-binary-indexed-tree');

var bit = new BinaryIndexedTree({ defaultFrequency: 10, maxVal: 10 });

// Read a single frequency
// Output: 10
console.log(bit.readSingle(3));

// Update the frequency by delta
// Output: 15
bit.update(2, 5);
console.log(bit.readSingle(2));

// Write a single frequency
// Output: 20
bit.writeSingle(3, 20);
console.log(bit.readSingle(3));

// Read the cumulated frequency
// Output: 55
console.log(bit.read(4));

// Find the lower bound
// Output: 3
console.log(bit.lowerBound(55));

// Find the upper bound
// Output: 4
console.log(bit.upperBound(55));

MIT

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