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algm

v0.1.9

Published

[![NPM version][npm-image]][npm-url] [![npm download][download-image]][download-url] [![ci][ci-image]][ci-url]

Downloads

63

Readme

algm

NPM version npm download ci

A fast algorithm library for JavaScript/TypeScript.

Problem

When you participate in an algorithm competition or code algorithm problems online such as leetcode, you may choose c++,java,python. Because they have the built-in library like STL that contains priority queue,order set etc.

Installation

npm install algm

Documentation

You can find the algm documentation on the website.

Why algm?

Safe

import a from 'algm';
const arr = Array(125625).fill(0);
//Maximum call stack size exceeded in nodejs
Math.max(...arr);
//safe
a.max(arr);

// the recursive version postorder traversal may result in maximum call stack error
// a.postorder internal use iteration
a.postorder(root, (node, fatherNode) => {
  console.log(node);
});

Contains many frequently used functions

import a from 'algm';
// init an array with an initial value of 0
a.initArray(4); // => [0,0,0,0]

// init a two-dimensional array with an initial value of 0
a.init2Array(3, 4); // => [[0,0,0,0],[0,0,0,0],[0,0,0,0]]

// get the max value
a.max(1, 3, 2); // => 3
a.max([1, 3, 2]); // => 3

// get the min value
a.min(1, 3, 2); // => 1
a.min([1, 3, 2]); // => 1

// compute the sum of an array
a.sum([1, 2, 3]); // => 6

// get the last element of an array
a.last([3, 2, 1]); // => 1

// return a new arr that does not contains duplicate elements.
a.unique([1, 1, 2, 2, 2, 6, 1]); //=> [1,2,6]

// sort the array in ascending order
a.sortA([3, 1, 2]); // => [1, 2, 3]
a.sortA([{ height: 3 }, { height: 2 }, { height: 1 }], x => x.height);
// => [{ height: 1 }, { height: 2 }, { height: 3 }]

a.sortD([3, 1, 2]); // => [3, 2, 1]
a.sortD([{ height: 3 }, { height: 2 }, { height: 1 }], x => x.height);
// => [{ height: 3 }, { height: 2 }, { height: 1 }]

// compute the greatest common divisor of a and b
a.gcd(4, 2); // => 2
a.gcd(9, 6); // => 3

// Randomly returns integers in [min, max)
a.random(2, 8); // => 4

// Compute the number of permutations c(n,m)=n*(n-1)*...(n-m+1)/(m!)
// the result is bigint
a.c(5, 2); // => 10n
a.c(5, 0); // => 1n

// Compute the number of permutations,
// then take the remainder of modulo 10 * * 9 + 7
a.cm(5, 2); // => 10
a.cm(5, 0); // => 1

// Compute the remainder of m mod n
// The main difference with m%n is that a.mod always return nonnegative number.
a.mod(2, 3); // => 2
a.mod(-2, 3); // => 1
-2 % 3; // => -2
a.mod(-2, 2); // => 0

data structure

  • priority queue

    max priority queue

    const input = [4, 3, 1];
    const maxP = new MaxPQ(input);
    maxP.max(); //=> 4
    maxP.insert(5);
    maxP.max(); //=> 5
    maxP.insert(8);
    maxP.max(); //=> 8
    maxP.delMax();
    maxP.max(); //=> 5

    Provide the specified key

    const input = [
      { name: 'xiao', age: 21 },
      { name: 'wang', age: 22 },
      { name: 'li', age: 25 },
    ];
    const maxP = new MaxPQ(input, v => v.age);
    const m = maxP.max(); //=> { name: 'li', age: 25 }
  • SkipList

    a probabilistic data structure

    search, insert, remove achieve O(Logn) expected performance. max,min cost O(1) time complexity

    const sl = new SkipList();
    sl.insert(3);
    sl.insert(1);
    sl.insert(5);
    sl.search(1); // => 1
    sl.remove(1);
    sl.search(1); // => null
  • randomized binary search tree

    search, insert, remove, find the k-th max value achieve O(Logn) expected performance.

    const rbst = new RBST();
    const arr = [1, 7, 3];
    arr.forEach(v => {
      rbst.insert(v);
    });
    rbst.search(3); // => 3
    rbst.findKMax(1); // => 7
    rbst.remove(3);
    rbst.search(3); // => null
    rbst.findKMax(2); // => 1
  • Segment tree

    Max segment tree

    Query the maximum value of given range and update the value in O(Logn) time.

    import { MaxArr } from 'algm';
    const maxArr = new MaxArr([2, 3, 1, 7, 9]);
    const [l, r] = [0, 2];
    // find the maximum value from [l,r]
    maxArr.query(l, r); //=> 3
    maxArr.query(0, 3); //=> 7
    maxArr.update(1, 9); // arr=[2, 9, 1, 7, 9]
    maxArr.query(0, 3); //=> 9

    Provide the specified key

    import { MaxArr } from 'algm';
    const maxArr = new MaxArr(
      [
        { name: 'li', age: 21 },
        { name: 'wang', age: 24 },
        { name: 'xx', age: 23 },
      ],
      node => node.age
    );
    maxArr.query(0, 2); //=> { name: 'wang', age: 24 }
    maxArr.update(0, { name: 'xiao', age: 25 });
    maxArr.query(0, 2); //=> { name: 'xiao', age: 25 }

    sum segment tree

    Query the sum of given range and update the value in O(Logn) time.

    import { SumArr } from 'algm';
    const sumArr = new SumArr([2, 3, 1, 7, 9]);
    sumArr.query(0, 2); //=> 6
    sumArr.update(2, 4);
    sumArr.query(0, 2); //=> 9

    value segment tree

    Given an array contains all the values,insert the value one by one,and query the number of value in [lower,upper].

    import { ValueArr } from 'algm';
    const arr = [1, 2, 3, 5, 7];
    const vArr = new ValueArr(arr);
    vArr.insert(1);
    vArr.insert(3);
    vArr.insert(5);
    assert.strictEqual(vArr.query(1, 5), 3);
    vArr.insert(1);
    assert.strictEqual(vArr.query(1, 5), 4);
  • union–find

    A data structure that stores a collection of disjoint (non-overlapping) sets. It provides operations for merging sets (union), and finding a representative member(find) of a set.

    import { UnionFind } from 'algm';
    const n = 4;
    const uf = new UnionFind(n);
    uf.union(0, 1);
    uf.union(1, 2);
    uf.isSameSet(0, 2); //=> true
    uf.isSameSet(0, 3); //=> false

algorithm

  • topsort

    topsort({
      n: 5,
      edges: [
        [1, 0],
        [1, 3],
        [3, 2],
        [3, 4],
      ],
    }); // => [1,3,4,2,0]
  • Hopcroft–Karp algorithm

    a fast bipartite matching algorithms

    hopcroftKarp(5, [
      [5, 6],
      [5, 9],
      [7, 8],
      [5, 9],
      [6, 8],
    ]);
    // => Map(10){ 0=>6,1=>9,2=>7,3=>5,4=>8,6=>0,7=>2,8=>4,9=>1 }
  • manacher a linear time algorithm to find all the palindromic substring

  import { getPalindromeArr } from 'algm';
  const  palindromeLengthArr=getPalindromeArr('aba')
  // The length of the palindrome centered on each vertex
  // => [1,3,1]