#995 - Minimum Number of K Consecutive Bit Flips

Hard • View on LeetCode • View on GitHub

Array Bit Manipulation Prefix Sum Sliding Window Queue

Problem Description

You are given a binary array nums and an integer k.

A k-bit flip is choosing a subarray of length k from nums and simultaneously changing every 0 in the subarray to 1, and every 1 in the subarray to 0.

Return the minimum number of k-bit flips required so that there is no 0 in the array. If it is not possible, return -1.

A subarray is a contiguous part of an array.

Solution

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var minKBitFlips = function(nums, k) {
  const queue = [];
  let flipCount = 0;
  let result = 0;

  for (let i = 0; i < nums.length; i++) {
    if (queue.length && queue[0] === i) {
      queue.shift();
      flipCount--;
    }

    if ((nums[i] + flipCount) % 2 === 0) {
      if (i + k > nums.length) return -1;
      result++;
      flipCount++;
      queue.push(i + k);
    }
  }

  return result;
};