一、无重叠区间

var eraseOverlapIntervals = function(intervals) {
    if(intervals.lenght === 0) {
      return 0
  }
  intervals.sort((a, b) => a[1] - b[1])
  let right = intervals[0][1]
  let ans = 0
  let n = intervals.length
  for(let i = 1;i < n;i++){
      if(intervals[i][0] >= right) {
        ans++
      right = intervals[i][1]
    }
    return n - ans
  }
};