largest-number-at-least-twice-of-others.js

/**
 * Largest Number At Least Twice of Others
 *
 * In a given integer array nums, there is always exactly one largest element.
 *
 * Find whether the largest element in the array is at least twice as much as every other number in the array.
 *
 * If it is, return the index of the largest element, otherwise return -1.
 *
 * Example 1:
 *
 * Input: nums = [3, 6, 1, 0]
 * Output: 1
 * Explanation: 6 is the largest integer, and for every other number in the array x,
 * 6 is more than twice as big as x.  The index of value 6 is 1, so we return 1.
 *
 *
 * Example 2:
 *
 * Input: nums = [1, 2, 3, 4]
 * Output: -1
 * Explanation: 4 isn't at least as big as twice the value of 3, so we return -1.
 */

/**
 * @param {number[]} nums
 * @return {number}
 */
var dominantIndex = function(nums) {
  let first = nums[0];
  let second = -Infinity;
  let maxIndex = 0;

  for (let i = 1; i < nums.length; i++) {
    if (nums[i] >= first) {
      second = first;
      first = nums[i];
      maxIndex = i;
    } else if (nums[i] > second) {
      second = nums[i];
    }
  }

  return first >= second * 2 ? maxIndex : -1;
};

export { dominantIndex };