📝 Add docstrings to auto-fix-missing-headers-20260408

Docstrings generation was requested by @tkzzzzzz6.

The following files were modified:

* `hello.cpp`
* `leetcode/Study Plan/3432. 统计元素和差值为偶数的分区方案/1.cpp`

Author: coderabbitai[bot]

hello.cpp

@@ -1,6 +1,13 @@
 #include <iostream>
 using namespace std;
 
+/**
+ * @brief Writes a fixed greeting to standard output and exits.
+ *
+ * Prints the string "Hello, Algorithm_beginner_learning_notes!" followed by a newline to stdout.
+ *
+ * @return int `0` on successful program termination.
+ */
 int main() {
     cout << "Hello, Algorithm_beginner_learning_notes!" << endl;
     return 0;

leetcode/Study Plan/3432. 统计元素和差值为偶数的分区方案/1.cpp

@@ -2,6 +2,12 @@
 #include <numeric>
 class Solution {
     public:
+        /**
+         * @brief Compute a partition-count value determined by whether the sum of `nums` is odd or even.
+         *
+         * @param nums Input vector of integers whose elements are summed.
+         * @return int `0` if the total sum of `nums` is odd; otherwise `nums.size() - 1` (which is `-1` for an empty vector).
+         */
         int countPartitions(vector<int>& nums) {
             int sum = reduce(nums.begin(),nums.end());
             return sum % 2 ? 0 : nums.size() - 1;