e100: Add cpp impl of share candy

src/od/2024e100/share-candy/.gitignore

@@ -0,0 +1 @@
+/solution

src/od/2024e100/share-candy/Makefile

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+
+solution: solution.cpp
+	g++ solution.cpp -o solution

src/od/2024e100/share-candy/index.md

@@ -58,6 +58,12 @@
 {{#include solution.py:6:}}
 ```
 
+### C++
+
+```cpp
+{{#include solution.cpp:5:}}
+```
+
 ### Rust
 
 ```rust

src/od/2024e100/share-candy/solution.cpp

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+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+#include <iostream>
+#include <unordered_map>
+
+// 缓存 + 递归
+int get_minimum_times(int num, std::unordered_map<int, int>& cache) {
+  const auto iter = cache.find(num);
+  if (iter != cache.end()) {
+    return iter->second;
+  }
+
+  if (num % 2 == 0) {
+    // 如果是偶数个
+    // 平均分一次
+    const int times = 1 + get_minimum_times(num / 2, cache);
+    cache[num] = times;
+    return times;
+  } else {
+    // 如果是奇数个, 有两种方式:
+    // 取一个
+    const int times1 = 1 + get_minimum_times(num + 1, cache);
+    // 放一个
+    const int times2 = 1 + get_minimum_times(num - 1, cache);
+
+    // 求它们的最小值
+    const int min_times = std::min(times1, times2);
+    cache[num] = min_times;
+    return min_times;
+  }
+}
+
+int main() {
+  std::unordered_map<int, int> cache;
+  cache[1] = 0;
+
+  int num_candies = 0;
+  std::cin >> num_candies;
+
+  const int times = get_minimum_times(num_candies, cache);
+  std::cout << times << std::endl;
+
+  return 0;
+}