#3097 - Shortest Subarray With OR at Least K II

Medium • View on LeetCode • View on GitHub

Problem Description

You are given an array nums of non-negative integers and an integer k.

An array is called special if the bitwise OR of all of its elements is at least k.

Return the length of the shortest special non-empty subarray of nums, or return -1 if no special subarray exists.

Solution

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var minimumSubarrayLength = function(nums, k) {
  if (k === 0) return 1;

  const bitCounts = new Array(32).fill(0);
  let minLength = Infinity;
  let orValue = 0;
  let left = 0;

  for (let right = 0; right < nums.length; right++) {
    const num = nums[right];
    for (let bit = 0; bit < 32; bit++) {
      if (num & (1 << bit)) bitCounts[bit]++;
      if (bitCounts[bit] > 0) orValue |= 1 << bit;
    }

    while (orValue >= k && left <= right) {
      minLength = Math.min(minLength, right - left + 1);
      const leftNum = nums[left];
      for (let bit = 0; bit < 32; bit++) {
        if (leftNum & (1 << bit)) {
          bitCounts[bit]--;
          if (bitCounts[bit] === 0) orValue &= ~(1 << bit);
        }
      }
      left++;
    }
  }

  return minLength === Infinity ? -1 : minLength;
};