C语言实现二叉树的搜索及相关算法示例

#include<stack>
#include<queue>
using namespace std;
class tree_node{
public:
  int key;
  tree_node *left;
  tree_node *right;
  int tag;
  tree_node(){
    key = 0;
    left = right = NULL;
    tag = 0;
  }
  ~tree_node(){}
};
void visit(int value){
  printf("%d\n", value);
}
// 插入
tree_node * insert_tree(tree_node *root, tree_node* node){
  if (!node){
    return root;
  }
  if (!root){
    root = node;
    return root;
  }
  tree_node * p = root;
  while (p){
    if (node->key < p->key){
      if (p->left){
        p = p->left;
      }
      else{
        p->left = node;
        break;
      }
    }
    else{
      if (p->right){
        p = p->right;
      }
      else{
        p->right = node;
        break;
      }
    }
  }
  return root;
}
// 查询key所在node
tree_node* search_tree(tree_node* root, int key){
  tree_node * p = root;
  while (p){
    if (key < p->key){
      p = p->left;
    }
    else if (key > p->key){
      p = p->right;
    }
    else{
      return p;
    }
  }
  return NULL;
}
// 创建树
tree_node* create_tree(tree_node *t, int n){
  tree_node * root = t;
  for (int i = 1; i<n; i++){
    insert_tree(root, t + i);
  }
  return root;
}
// 节点前驱
tree_node* tree_pre(tree_node* root){
  if (!root->left){ return NULL; }
  tree_node* p = root->left;
  while (p->right){
    p = p->right;
  }
  return p;
}
// 节点后继
tree_node* tree_suc(tree_node* root){
  if (!root->right){ return NULL; }
  tree_node* p = root->right;
  while (p->left){
    p = p->left;
  }
  return p;
}
// 中序遍历
void tree_walk_mid(tree_node *root){
  if (!root){ return; }
  tree_walk_mid(root->left);
  visit(root->key);
  tree_walk_mid(root->right);
}
// 中序遍历非递归
void tree_walk_mid_norecursive(tree_node *root){
  if (!root){ return; }
  tree_node* p = root;
  stack<tree_node*> s;
  while (!s.empty() || p){
    while (p){
      s.push(p);
      p = p->left;
    }
    if (!s.empty()){
      p = s.top();
      s.pop();
      visit(p->key);
      p = p->right;
    }
  }
}
// 前序遍历
void tree_walk_pre(tree_node *root){
  if (!root){ return; }
  visit(root->key);
  tree_walk_pre(root->left);
  tree_walk_pre(root->right);
}
// 前序遍历非递归
void tree_walk_pre_norecursive(tree_node *root){
  if (!root){ return; }
  stack<tree_node*> s;
  tree_node* p = root;
  s.push(p);
  while (!s.empty()){
    tree_node *node = s.top();
    s.pop();
    visit(node->key);
    if (node->right){
      s.push(node->right);
    }
    if (node->left){
      s.push(node->left);
    }
  }
}
// 后序遍历
void tree_walk_post(tree_node *root){
  if (!root){ return; }
  tree_walk_post(root->left);
  tree_walk_post(root->right);
  visit(root->key);
}
// 后序遍历非递归
void tree_walk_post_norecursive(tree_node *root){
  if (!root){ return; }
  stack<tree_node*> s;
  s.push(root);
  while (!s.empty()){
    tree_node * node = s.top();
    if (node->tag != 1){
      node->tag = 1;
      if (node->right){
        s.push(node->right);
      }
      if (node->left){
        s.push(node->left);
      }
    }
    else{
      visit(node->key);
      s.pop();
    }
  }
}
// 层级遍历非递归
void tree_walk_level_norecursive(tree_node *root){
  if (!root){ return; }
  queue<tree_node*> q;
  tree_node* p = root;
  q.push(p);
  while (!q.empty()){
    tree_node *node = q.front();
    q.pop();
    visit(node->key);
    if (node->left){
      q.push(node->left);
    }
    if (node->right){
      q.push(node->right);
    }
  }
}
// 拷贝树
tree_node * tree_copy(tree_node *root){
  if (!root){ return NULL; }
  tree_node* newroot = new tree_node();
  newroot->key = root->key;
  newroot->left = tree_copy(root->left);
  newroot->right = tree_copy(root->right);
  return newroot;
}
// 拷贝树
tree_node * tree_copy_norecursive(tree_node *root){
  if (!root){ return NULL; }
  tree_node* newroot = new tree_node();
  newroot->key = root->key;
  stack<tree_node*> s1, s2;
  tree_node *p1 = root;
  tree_node *p2 = newroot;
  s1.push(root);
  s2.push(newroot);
  while (!s1.empty()){
    tree_node* node1 = s1.top();
    s1.pop();
    tree_node* node2 = s2.top();
    s2.pop();
    if (node1->right){
      s1.push(node1->right);
      tree_node* newnode = new tree_node();
      newnode->key = node1->right->key;
      node2->right = newnode;
      s2.push(newnode);
    }
    if (node1->left){
      s1.push(node1->left);
      tree_node* newnode = new tree_node();
      newnode->key = node1->left->key;
      node2->left = newnode;
      s2.push(newnode);
    }
  }
  return newroot;
}
int main(){
  tree_node T[6];
  for (int i = 0; i < 6; i++){
    T[i].key = i*2;
  }
  T[0].key = 5;
  tree_node* root = create_tree(T, 6);
  //tree_walk_mid(root);
  //tree_walk_mid_norecursive(root);
  //tree_walk_pre(root);
  //tree_walk_pre_norecursive(root);
  //tree_walk_post(root);
  //tree_walk_post_norecursive(root);
  //tree_walk_level_norecursive(root);
  visit(search_tree(root, 6)->key);
  visit(tree_pre(root)->key);
  visit(tree_suc(root)->key);
  //tree_node* newroot = tree_copy_norecursive(root);
  //tree_walk_mid(newroot);
  return 0;
}
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