mathball/lib/pow/index.js

A JavaScript library for Competitive Programming

"use strict";

/*
    Function: pow(base,exp,modulo)
*/

var validate = require("../validation/non-negative-integer");

function pow(base, exp) {
    var modulo = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : Number.MAX_SAFE_INTEGER;


    var result = 1;

    base = base % modulo;

    while (exp > 0) {
        if (exp % 2 == 1) {
            result = result * base % modulo;
        }

        exp = exp / 2 | 0;

        base = base * base % modulo;
    }
    return result;
}

module.exports = function (base, exp, modulo) {

    validate(base, "pow");
    validate(exp, "pow");

    if (typeof modulo === "undefined") {
        return pow(base, exp);
    } else {
        validate(modulo, "pow");
        return pow(base, exp, modulo);
    }
};