求二叉树第k层的节点个数
typedef struct Node{int val;struct Node* _left;struct Node* _right;Node(const int& data):val(data), _left(NULL), _right(NULL){}}Node;void _GetKLevelSize(Node* root, const size_t k,size_t level, size_t& count){if (root == NULL){return;}if (level == k){count++;return;}_GetKLevelSize(root->_left, k, level + 1, count);_GetKLevelSize(root->_right, k, level + 1, count);}size_t GetKLevelSize(size_t k){assert(k > 0);size_t count = 0;size_t level = 1;_GetKLevelSize(_root, k, level, count);return count;}typedef struct Node{int val;stru 
