From c3955ad3909540854b0e51771529ee61386d5a72 Mon Sep 17 00:00:00 2001 From: MH Hung Date: Fri, 5 Sep 2025 16:52:45 +0800 Subject: [PATCH] docs(makeTheIntegerZero): add README --- .../README.md | 101 ++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 problems/2749-minimum-operations-to-make-the-integer-zero/README.md diff --git a/problems/2749-minimum-operations-to-make-the-integer-zero/README.md b/problems/2749-minimum-operations-to-make-the-integer-zero/README.md new file mode 100644 index 0000000..253e45d --- /dev/null +++ b/problems/2749-minimum-operations-to-make-the-integer-zero/README.md @@ -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