lowbit

Author: masx200

range-sum-query-mutable/NumArray.ts

@@ -1,3 +1,6 @@
+export function lowbit(x: number) {
+    return x & -x;
+}
 const add = Symbol();
 export default class NumArray {
     #tree: number[];
@@ -12,12 +15,10 @@ export default class NumArray {
     [add](index: number, val: number) {
         while (index < this.#tree.length) {
             this.#tree[index] += val;
-            index += this.#lowBit(index);
+            index += lowbit(index);
         }
     }
-    #lowBit(x: number) {
-        return x & -x;
-    }
+
     update(index: number, val: number): void {
         this[add](index + 1, val - this.#nums[index]);
         this.#nums[index] = val;
@@ -30,7 +31,7 @@ export default class NumArray {
         let sum = 0;
         while (index > 0) {
             sum += this.#tree[index];
-            index -= this.#lowBit(index);
+            index -= lowbit(index);
         }
         return sum;
     }

rank-from-stream-lcci/BinaryIndexTree.ts

@@ -1,9 +1,7 @@
 export class BinaryIndexTree<T = number> {
     defaultValue: T;
     operation: (existing: T, applied: T) => T;
-    static lowbit(x: number) {
-        return x & -x;
-    }
+
     #tree: T[];
     constructor(
         public size: number,
@@ -23,15 +21,18 @@ export class BinaryIndexTree<T = number> {
         this.defaultValue = defaultValue;
     }
     update(i: number, value: T) {
-        for (let p = i; p <= this.size; p += BinaryIndexTree.lowbit(p)) {
+        for (let p = i; p <= this.size; p += lowbit(p)) {
             this.#tree[p] = this.operation(this.#tree[p], value);
         }
     }
     query(n: number) {
         let ans = this.defaultValue;
-        for (let p = n; p > 0; p -= BinaryIndexTree.lowbit(p)) {
+        for (let p = n; p > 0; p -= lowbit(p)) {
             ans = this.operation(ans, this.#tree[p]);
         }
         return ans;
     }
 }
+export function lowbit(x: number) {
+    return x & -x;
+}