c++有关类成员函数

Question

 struct TreeNode {
     int val;
      TreeNode *left;
    TreeNode *right;
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}//疑惑在这
  };

请问疑惑的地方，如果不简写，展开来写，是什么样的？想知道这个

Answer 1

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x, TreeNode *left, TreeNode *right) 
    {
        val=x;
        this->left=left;
        this->right=right;
    } //val(x), left(left), right(right) {}//疑惑在这
};