最长递增子序列（LIS）：求数组中最长严格递增子序列长度。

function lengthOfLIS(nums) {
  const tails = []
  for (const x of nums) {
    let lo = 0, hi = tails.length
    while (lo < hi) {
      const mid = (lo + hi) >> 1
      if (tails[mid] < x) lo = mid + 1
      else hi = mid
    }
    tails[lo] = x
  }
  return tails.length
}