优化

src/AStar.js

@@ -0,0 +1,126 @@
+import { checkIsSamePoint, getNextPoints } from "./utils";
+
+// A*算法类
+export default class AStar {
+ constructor() {
+ this.startPoint = null;
+ this.endPoint = null;
+ this.pointList = [];
+ this.openList = [];
+ this.closeList = [];
+ }
+
+ // 算法主流程
+ start(startPoint, endPoint, pointList) {
+ this.startPoint = startPoint;
+ this.endPoint = endPoint;
+ this.pointList = pointList;
+ this.openList = [
+ {
+ point: this.startPoint, // 起点加入openList
+ cost: 0, // 代价
+ parent: null, // 父节点
+ },
+ ];
+ this.closeList = [];
+ while (this.openList.length) {
+ let point = this.getBestPoint();
+ if (!point) {
+ return [];
+ }
+ // point为终点，那么算法结束，输出最短路径
+ if (checkIsSamePoint(point.point, this.endPoint)) {
+ return this.getRoutes(point);
+ } else {
+ // 将point从openList中删除
+ this.removeFromOpenList(point);
+ // 将point添加到closeList中
+ this.closeList.push(point);
+ // 遍历point周围的点
+ let nextPoints = getNextPoints(point.point, this.pointList);
+ for (let i = 0; i < nextPoints.length; i++) {
+ let cur = nextPoints[i];
+ // 如果该点在closeList中，那么跳过该点
+ if (this.checkIsInList(cur, this.closeList)) {
+ continue;
+ } else if (!this.checkIsInList(cur, this.openList)) {
+ // 如果该点也不在openList中
+ let pointObj = {
+ point: cur,
+ parent: point,
+ cost: 0,
+ };
+ this.computeCost(pointObj);
+ this.openList.push(pointObj);
+ }
+ }
+ }
+ }
+ return [];
+ }
+
+ // 获取openList中优先级最高的点
+ getBestPoint() {
+ let min = Infinity;
+ let point = null;
+ this.openList.forEach((item) => {
+ if (item.cost < min) {
+ point = item;
+ min = item.cost;
+ }
+ });
+ return point;
+ }
+
+ // 从point出发，找出其所有祖宗节点，也就是最短路径
+ getRoutes(point) {
+ let res = [point];
+ let par = point.parent;
+ while (par) {
+ res.unshift(par);
+ par = par.parent;
+ }
+ return res.map((item) => {
+ return item.point;
+ });
+ }
+
+ // 将点从openList中删除
+ removeFromOpenList(point) {
+ let index = this.openList.findIndex((item) => {
+ return checkIsSamePoint(point.point, item.point);
+ });
+ this.openList.splice(index, 1);
+ }
+
+ // 检查点是否在列表中
+ checkIsInList(point, list) {
+ return list.find((item) => {
+ return checkIsSamePoint(item.point, point);
+ });
+ }
+
+ // 计算一个点的代价
+ computeCost(point) {
+ point.cost = this.computedGCost(point) + this.computedHCost(point);
+ }
+
+ // 计算代价g(n)
+ computedGCost(point) {
+ let res = 0;
+ let par = point.parent;
+ while (par) {
+ res += par.cost;
+ par = par.parent;
+ }
+ return res;
+ }
+
+ // 计算代价h(n)
+ computedHCost(point) {
+ return (
+ Math.abs(this.endPoint[0] - point.point[0]) +
+ Math.abs(this.endPoint[1] - point.point[1])
+ );
+ }
+}