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94 lines
2.9 KiB
94 lines
2.9 KiB
import type { Cell } from './Cell';
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import { cellKey } from './Cell';
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import type { GridMap } from './GridMap';
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import { createMembershipSet, membershipAdd } from '../../../tools/MembershipSet';
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const ORTH: readonly { dr: number; dc: number }[] = [
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{ dr: -1, dc: 0 },
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{ dr: 1, dc: 0 },
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{ dr: 0, dc: -1 },
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{ dr: 0, dc: 1 },
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];
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/**
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* 从当前可走格构建唯一正交闭环（外围环走）。
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* 要求：可走格构成简单环（每格恰好 2 个正交可走邻居），并按顺时针定向。
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* @returns 有序闭环（不含重复起点）；无法建环返回 null
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*/
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export function buildPatrolLoopFromWalkable(grid: GridMap): Cell[] | null {
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const walkable: Cell[] = [];
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for (let row = 0; row < grid.rows; row++) {
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for (let col = 0; col < grid.cols; col++) {
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const cell = { row, col };
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if (grid.isWalkable(cell)) walkable.push(cell);
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}
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}
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if (walkable.length < 4) return null;
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const walkSet = createMembershipSet<string>();
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for (const c of walkable) membershipAdd(walkSet, cellKey(c));
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const neighbors = (c: Cell): Cell[] => {
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const out: Cell[] = [];
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for (const d of ORTH) {
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const nb = { row: c.row + d.dr, col: c.col + d.dc };
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if (!grid.inBounds(nb)) continue;
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if (!walkSet.has(cellKey(nb))) continue;
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out.push(nb);
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}
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return out;
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};
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for (const c of walkable) {
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if (neighbors(c).length !== 2) return null;
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}
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let start = walkable[0];
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for (const c of walkable) {
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if (c.row < start.row || (c.row === start.row && c.col < start.col)) {
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start = c;
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}
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}
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const startNbs = neighbors(start);
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// 顺时针：外环左上角优先向右，其次向下
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let first: Cell | null = null;
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for (const prefer of [
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{ row: start.row, col: start.col + 1 },
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{ row: start.row + 1, col: start.col },
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{ row: start.row, col: start.col - 1 },
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{ row: start.row - 1, col: start.col },
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]) {
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if (startNbs.some((n) => n.row === prefer.row && n.col === prefer.col)) {
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first = prefer;
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break;
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}
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}
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if (!first) return null;
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const loop: Cell[] = [{ ...start }];
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let prev = start;
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let cur = first;
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const maxStep = walkable.length + 2;
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for (let step = 0; step < maxStep; step++) {
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loop.push({ ...cur });
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if (cur.row === start.row && cur.col === start.col) {
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// 回到起点：去掉末尾重复起点
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loop.pop();
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break;
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}
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const nbs = neighbors(cur);
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let next: Cell | null = null;
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for (const n of nbs) {
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if (n.row === prev.row && n.col === prev.col) continue;
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next = n;
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break;
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}
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if (!next) return null;
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prev = cur;
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cur = next;
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}
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if (loop.length !== walkable.length) return null;
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return loop;
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}
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