tweak

graph.js

@@ -0,0 +1,34 @@
+export class MinHeap {
+  constructor() { this.items = []; }
+  push(item) {
+    this.items.push(item);
+    let i = this.items.length - 1;
+    while (i > 0) {
+      const parent = (i - 1) >> 1;
+      if (this.items[parent].f <= item.f) break;
+      this.items[i] = this.items[parent];
+      i = parent;
+    }
+    this.items[i] = item;
+  }
+  pop() {
+    if (this.items.length === 0) return null;
+    const root = this.items[0];
+    const last = this.items.pop();
+    if (this.items.length > 0) {
+      let i = 0;
+      while (true) {
+        const left = i * 2 + 1;
+        const right = left + 1;
+        if (left >= this.items.length) break;
+        const child = right < this.items.length && this.items[right].f < this.items[left].f ? right : left;
+        if (this.items[child].f >= last.f) break;
+        this.items[i] = this.items[child];
+        i = child;
+      }
+      this.items[i] = last;
+    }
+    return root;
+  }
+  get length() { return this.items.length; }
+}