mathball/lib/modInv/index.js

A JavaScript library for Competitive Programming

'use strict';

/* Modular Multiplicative Inverse
* function : modInv()
*/

var validate = require('../validation/integer');

var gcd = require('../gcd');

function modInv(a, m) {
	var arr = [a, m];
	if (gcd(arr) == 1) {
		for (var i = 1; i < m; i++) {
			if (a * i % m == 1) return i;
		}
	} else return 0;
}

exports.modInv = function (a, m) {
	validate(a, 'modInv');
	validate(m, 'modInv');
	return modInv(a, m);
};