#2961 - Double Modular Exponentiation

Medium • View on LeetCode • View on GitHub

Problem Description

You are given a 0-indexed 2D array variables where variables[i] = [ai, bi, ci, mi], and an integer target.

An index i is good if the following formula holds:

0 <= i < variables.length
((aibi % 10)ci) % mi == target

Return an array consisting of good indices in any order.

Solution

/**
 * @param {number[][]} variables
 * @param {number} target
 * @return {number[]}
 */
var getGoodIndices = function(variables, target) {
  const result = [];

  for (let i = 0; i < variables.length; i++) {
    const [base, exp1, exp2, modulus] = variables[i];

    let inner = 1;
    for (let j = 0; j < exp1; j++) {
      inner = (inner * base) % 10;
    }

    let count = 1;
    for (let j = 0; j < exp2; j++) {
      count = (count * inner) % modulus;
    }

    if (count === target) {
      result.push(i);
    }
  }

  return result;
};