一个漂亮的打印二叉树的程序-ag真人游戏

写二叉树的程序时经常会遇到希望漂亮地把二叉树给输出，本文给出了一个小程序。

以下时打印的效果：

// ag真人试玩娱乐 copyright @ l.j.shou jan.16, 2014
// a fancy binary tree printer
#ifndef binary_tree_printer_h_
#define binary_tree_printer_h_
#include 
#include 
#include 
using std::vector;
using std::cout;
using std::endl;
using std::max;
void printbinarytree(treenode *root);
struct treenode
{
  treenode *left;
  treenode *right;
  int val;
  treenode(int x=0)
   : val(x), left(null), right(null){}
};
static int maxlevel(treenode *root)
{
  if(root == null) return 0;
  return max(maxlevel(root->left), maxlevel(root->right))   1;
}
// test whether all elements in vector are null
static bool isallelementsnull(const vector &nodes)
{
  vector::const_iterator it = nodes.begin();
  while(it != nodes.end()){
    if(*it) return false; 
      it;
  }
  return true;
}
static void printwhitespaces(int num)
{
  for(int i=0; i &nodes, int level, int max_level)
{
  if(nodes.empty() || isallelementsnull(nodes)) return; // exit
  int floor = max_level - level;
  int endge_lines = 1 << (max(floor-1, 0));
  int first_spaces = (1 << floor) - 1;
  int between_spaces = (1 << (floor 1)) - 1;
  printwhitespaces(first_spaces);
  // print the 'level' level 
  vector new_nodes;
  vector::const_iterator it = nodes.begin();
  for(; it != nodes.end();   it){
    if(*it != null){
      cout << (*it)->val;
      new_nodes.push_back((*it)->left);
      new_nodes.push_back((*it)->right);
    }
    else{
      new_nodes.push_back(null);
      new_nodes.push_back(null);
      cout << " ";
    }
    printwhitespaces(between_spaces);
  }
  cout << endl;
  // print the following /s and \s
  for(int i=1; i<= endge_lines;   i){
    for(int j=0; jleft != null)
        cout << "/";
      else
        printwhitespaces(1);
      printwhitespaces(i i-1);
      
      if(nodes[j]->right != null)
        cout << "\\";
      else
        printwhitespaces(1);
      printwhitespaces(endge_lines   endge_lines - i);
    }
    cout << endl;
  }
  printnode(new_nodes, level 1, max_level);
}
// wrapper function
void printbinarytree(treenode *root)
{
  int max_level = maxlevel(root);
  vector nodes;
  
  nodes.push_back(root);
 
  printnode(nodes, 1, max_level);
}
#endif
#if 0
int main(void)
{
  treenode *root(null);
  
  root = new treenode(1);
  root->left = new treenode(2);
  root->right = new treenode(3);
  root->left->left = new treenode(4);
  root->right->right = new treenode(7);
  root->left->left->left = new treenode(8);
  root->left->left->right = new treenode(9);
  printbinarytree(root);
  root = destroy(root);
  return 0;
}
#endif