fix: TreeMultiSet delete

Author: upupming

test/treeset.spec.ts

@@ -56,5 +56,10 @@ describe('treeset', () => {
       set.add(10)
       expect(set.count(10)).toEqual(2)
     })
+    it('delete should only erase the value when count is 0', () => {
+      const set = new TreeMultiSet([4, 4])
+      set.delete(4)
+      expect(set.values().next().value).toEqual(4)
+    })
   })
 })

treeset.ts

@@ -128,8 +128,10 @@ class TreeMultiSet<T = number> {
   }
 
   delete (val: T): void {
-    this.tree.deleteByValue(val)
     this.decrease(val)
+    if (this.count(val) === 0) {
+      this.tree.deleteByValue(val)
+    }
     this.#size--
   }