239-SlideWindowMaximum.js

var maxSlidingWindow = function (nums, k) {
  const n = nums.length;
  const q = [];
  for (let i = 0; i < k; i++) {
    while (q.length && nums[i] >= nums[q[q.length - 1]]) {
      q.pop();
    }
    q.push(i);
  }

  const ans = [nums[q[0]]];
  for (let i = k; i < n; i++) {
    while (q.length && nums[i] >= nums[q[q.length - 1]]) {
      q.pop();
    }
    q.push(i);
    while (q[0] <= i - k) {
      q.shift();
    }
    ans.push(nums[q[0]]);
  }
  return ans;
};