docs(makeTheIntegerZero): add README
This commit is contained in:
@@ -0,0 +1,101 @@
|
||||
# [2749] Minimum Operations To Make The Integer Zero
|
||||
|
||||
## 題目資訊
|
||||
- **難度**: Medium
|
||||
- **標籤**: Bit Manipulation, Brainteaser, Enumeration
|
||||
- **題目連結**: [LeetCode](https://leetcode.com/problems/minimum-operations-to-make-the-integer-zero/)
|
||||
- **練習日期**: 2025-09-05
|
||||
|
||||
## 題目描述
|
||||
You are given two integers `num1` and `num2`.
|
||||
|
||||
In one operation, you can choose integer i in the range `[0, 60]` and subtract `2^i + num2` from `num1`.
|
||||
|
||||
Return the integer denoting the *minimum* number of operations needed to make `num1` equal to `0`.
|
||||
|
||||
If it is impossible to make `num1` equal to `0`, return `-1`.
|
||||
|
||||
## 解題思路
|
||||
|
||||
### 初步分析
|
||||
- 這題主要考察什麼概念?
|
||||
1. 位元操作 (Bit Manipulation):需要理解二進制表示和位元運算
|
||||
2. 數學建模:將實際問題轉換為數學等式
|
||||
3. 枚舉 (Enumeration):嘗試不同的操作次數 k
|
||||
4. 約束條件判斷:理解多個限制條件的邏輯關係
|
||||
- 有什麼關鍵限制條件?
|
||||
1. target ≥ 0
|
||||
2. bitCount(target) ≤ k
|
||||
3. k ≤ target
|
||||
- 預期時間/空間複雜度?
|
||||
- 時間複雜度:O(60 × log(target)) ≈ O(1)
|
||||
- 空間複雜度:O(1)
|
||||
|
||||
### 解法概述
|
||||
1. **解法**:
|
||||
- 思路:
|
||||
- 目標:讓 num1 變成 0
|
||||
- 每次操作:num1 = num1 - (2^i + num2)
|
||||
- k 次操作後:num1 - k*num2 - (2^i1 + 2^i2 + ... + 2^ik) = 0
|
||||
- 重新整理:target = num1 - k*num2 = 2^i1 + 2^i2 + ... + 2^ik
|
||||
- 時間複雜度:O(1)
|
||||
- 空間複雜度:O(1)
|
||||
|
||||
## 測試案例
|
||||
|
||||
### 範例輸入輸出
|
||||
```
|
||||
Input: num1 = 3, num2 = -2
|
||||
Output: 3
|
||||
Explanation:
|
||||
We can make 3 equal to 0 with the following operations:
|
||||
- We choose i = 2 and subtract 22 + (-2) from 3, 3 - (4 + (-2)) = 1.
|
||||
- We choose i = 2 and subtract 22 + (-2) from 1, 1 - (4 + (-2)) = -1.
|
||||
- We choose i = 0 and subtract 20 + (-2) from -1, (-1) - (1 + (-2)) = 0.
|
||||
It can be proven, that 3 is the minimum number of operations that we need to perform.
|
||||
```
|
||||
|
||||
### 邊界情況
|
||||
- `1 <= num1 <= 10^9`
|
||||
- `-10^9 <= num2 <= 10^9`
|
||||
|
||||
## 學習筆記
|
||||
|
||||
### 今天學到什麼?
|
||||
- 二位元的操作寫法
|
||||
|
||||
### 遇到的困難
|
||||
- 二位元的操作
|
||||
1. 方法一: 逐位檢查法
|
||||
- 程式碼:
|
||||
``` C#
|
||||
count += (int)(n & 1);
|
||||
n >>= 1;
|
||||
```
|
||||
- 運作原理:
|
||||
1. n & 1:檢查最右邊的位元是否為 1
|
||||
2. count += (int)(n & 1):如果是 1 就加到計數器
|
||||
3. n >>= 1:把 n 右移一位(去掉已檢查的位元)
|
||||
4. 重複直到 n 變成 0
|
||||
2. 方法二: 移除最右邊 1
|
||||
- 程式碼:
|
||||
``` C#
|
||||
count++;
|
||||
n &= n - 1;
|
||||
```
|
||||
- 運作原理:
|
||||
1. n - 1:讓最右邊的 1 變成 0,其右邊的 0 都變成 1
|
||||
2. n & (n - 1):神奇地移除了最右邊的 1
|
||||
3. count++:每移除一個 1,計數器就加 1
|
||||
4. 重複直到 n 變成 0
|
||||
|
||||
### 改善方向
|
||||
-
|
||||
|
||||
### 相關題目
|
||||
- [#991](https://leetcode.com/problems/broken-calculator) Broken Calculator
|
||||
- [#1658](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/) Minimum Operations to Reduce X to Zero
|
||||
|
||||
---
|
||||
**總結**:
|
||||
1. 學習二位元的使用技巧
|
Reference in New Issue
Block a user