查找链表的中间节点

typedef struct Node {
    int  data;
     Node*  next;
}Node;
  
Node* find_mid_node(Node* head) {
    //检查传入参数，防止空节点
    if (head)
        return head;
 
     //一步指针与两步指针
     Node* one_step = two_step = head;
 
     //当两步指针为NULL或者尾节点，一步指针就是中间节点
     while(two_step && two_step->next) {
          two_step = two_step->next->next;
          one_step = one_step->next;
     }
     
     return one_step;
}