电梯算法漫谈：当多台电梯开始协作

flowchart TD
    H["4 楼发出上行请求"] --> G["群控系统读取各台电梯状态"]
    G --> A["估算 A 的接人时间"]
    G --> B["估算 B 的接人时间"]
    G --> C["估算 C 的接人时间"]
    A --> S["比较候选方案"]
    B --> S
    C --> S
    S --> P["把请求分配给一台电梯"]
    P --> E["该电梯按自身规则运行"]

import { useState, type CSSProperties } from 'react';

type Direction = -1 | 0 | 1;
type Car = {
  id: string;
  floor: number;
  direction: Direction;
  stops: number[];
  passengers: number;
  capacity: number;
};

const CALL = { floor: 4, direction: 1 as const };
const FLOOR_TIME = 3;
const STOP_TIME = 8;

function estimateArrival(car: Car): number {
  if (car.passengers >= car.capacity) return Infinity;
  if (car.direction === 0) {
    return Math.abs(car.floor - CALL.floor) * FLOOR_TIME;
  }

  const forwardStops = car.stops
    .filter((floor) => (floor - car.floor) * car.direction > 0)
    .sort((a, b) => (a - b) * car.direction);
  const onTheWay =
    car.direction === CALL.direction &&
    (CALL.floor - car.floor) * car.direction >= 0;

  if (onTheWay) {
    const intermediateStops = forwardStops.filter(
      (floor) => (floor - CALL.floor) * car.direction < 0
    );
    return (
      Math.abs(CALL.floor - car.floor) * FLOOR_TIME +
      intermediateStops.length * STOP_TIME
    );
  }

  const turn = forwardStops[forwardStops.length - 1] ?? car.floor;
  return (
    (Math.abs(turn - car.floor) + Math.abs(CALL.floor - turn)) *
      FLOOR_TIME +
    forwardStops.length * STOP_TIME
  );
}

export default function Demo() {
  const [bDown, setBDown] = useState(true);
  const [cFull, setCFull] = useState(false);
  const cars: Car[] = [
    { id: 'A', floor: 1, direction: 0, stops: [], passengers: 0, capacity: 8 },
    { id: 'B', floor: 3, direction: bDown ? -1 : 0, stops: bDown ? [1] : [], passengers: 3, capacity: 8 },
    { id: 'C', floor: 6, direction: cFull ? -1 : 0, stops: cFull ? [1] : [], passengers: cFull ? 8 : 0, capacity: 8 },
  ];
  const results = cars.map((car) => ({ ...car, eta: estimateArrival(car) }));
  const chosen = results.filter((item) => Number.isFinite(item.eta))
    .sort((a, b) => a.eta - b.eta)[0];
  const nearest = results.reduce((a, b) =>
    Math.abs(a.floor - CALL.floor) <= Math.abs(b.floor - CALL.floor) ? a : b
  );

  const panel: CSSProperties = {
    border: '1px solid var(--c-border)', borderRadius: 10,
    padding: 12, background: 'var(--c-bg)',
  };

  return (
    <div style={{ fontFamily: 'var(--font-sans), sans-serif', color: 'var(--c-text)', fontSize: 14, maxWidth: 700, margin: '0 auto' }}>
      <div style={{ ...panel, background: 'var(--c-fill-subtle)', marginBottom: 12 }}>
        <strong>新请求：4 楼 · 上行 ↑</strong>
        <div style={{ color: 'var(--c-text-light)', fontSize: 12, marginTop: 4 }}>
          每层 3 秒；已有中途停靠每次加 8 秒。忽略加减速与未来新请求。
        </div>
      </div>
      <div style={{ display: 'flex', gap: 10, flexWrap: 'wrap', marginBottom: 12 }}>
        <label style={{ ...panel, flex: '1 1 190px', cursor: 'pointer' }}>
          <input type="checkbox" checked={bDown} onChange={(e) => setBDown(e.target.checked)} style={{ marginRight: 7 }} />
          B 正在下行，先到 1 楼
        </label>
        <label style={{ ...panel, flex: '1 1 160px', cursor: 'pointer' }}>
          <input type="checkbox" checked={cFull} onChange={(e) => setCFull(e.target.checked)} style={{ marginRight: 7 }} />
          C 已满载
        </label>
      </div>
      <div style={{ display: 'flex', gap: 10, flexWrap: 'wrap' }}>
        {results.map((car) => (
          <div key={car.id} style={{ ...panel, flex: '1 1 88px', minWidth: 0, borderColor: chosen?.id === car.id ? 'var(--c-primary)' : 'var(--c-border)' }}>
            <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', gap: 6 }}>
              <strong>{car.id} 电梯</strong>
              {chosen?.id === car.id && <span style={{ fontSize: 11, color: 'var(--c-primary)' }}>被选中</span>}
            </div>
            <div style={{ fontSize: 26, fontWeight: 700, margin: '6px 0' }}>{car.floor}F</div>
            <div style={{ fontSize: 12, color: 'var(--c-text-light)' }}>
              {car.passengers >= car.capacity ? '满载' : car.direction === 0 ? '空闲' : '下行，目标 1F'}
            </div>
            <div style={{ marginTop: 9, fontWeight: 600 }}>
              {Number.isFinite(car.eta) ? `预计 ${car.eta} 秒` : '不参与分配'}
            </div>
          </div>
        ))}
      </div>
      <div aria-live="polite" style={{ ...panel, background: 'var(--c-fill-subtle)', marginTop: 12, lineHeight: 1.7 }}>
        <div>离得最近的是 <strong>{nearest.id}</strong>（相距 {Math.abs(nearest.floor - CALL.floor)} 层）。</div>
        <div>预计到达最快的是 <strong>{chosen?.id ?? '无可用电梯'}</strong>{chosen ? `（${chosen.eta} 秒）` : ''}。</div>
      </div>
    </div>
  );
}