1
var SeatManager = function (n) {
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  this.min = 1;
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  this.n = n;
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  this.seat = [];
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};
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SeatManager.prototype.reserve = function () {
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  let res;
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  if (!this.seat[this.min]) {
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    res = this.min;
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    this.min = this.n < this.min ? NaN : this.min + 1;
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  } else {
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    res = this.min;
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    this.min = this.seat[this.min];
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  }
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  return res;
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};
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SeatManager.prototype.unreserve = function (seatNumber) {
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  if (this.min < seatNumber) {
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    let pre_inx = this.min;
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    let next_inx = this.seat[this.min];
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    while (next_inx < seatNumber) {
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      pre_inx = next_inx;
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      next_inx = this.seat[next_inx];
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    }
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    [this.seat[pre_inx], this.seat[seatNumber]] = [
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      seatNumber,
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      this.seat[pre_inx],
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    ];
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  } else {
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    [this.seat[seatNumber], this.min] = [this.min, seatNumber];
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  }
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};