Chinaunix首页 | 论坛 | 博客
  • 博客访问: 458797
  • 博文数量: 72
  • 博客积分: 1851
  • 博客等级: 上尉
  • 技术积分: 1464
  • 用 户 组: 普通用户
  • 注册时间: 2010-09-16 17:50
文章分类

全部博文(72)

文章存档

2013年(1)

2012年(17)

2011年(51)

2010年(3)

分类: C/C++

2011-08-13 19:41:21

 的具体好处(Linux内核中的调度器,内存管理,C++map等等),这里就不用多讲了,下面只是粘贴其具体的实现代码。
使用的数据结构:
  1. struct rb_node {
  2.   struct rb_node *parent;
  3.   struct rb_node *left;
  4.   struct rb_node *right;
  5.   unsigned int color:1;
  6.   long key;
  7. };

  8. struct rb_root {
  9.   struct rb_node *root;
  10.   unsigned long len;
  11. };
添加节点
具体的插入代码接口为:
  1. int rb_tree_insert(struct rb_root *root,struct rb_node *node)
  2. {
  3.     struct rb_node *p;
  4.         
  5.     _rb_tree_find(root,node,&p);
  6.     
  7.     if(p->key < node->key)
  8.     {
  9.      p->right = node;
  10.      node->parent = p;
  11.     }
  12.     else {
  13.      p->left = node;
  14.      node->parent = p;
  15.     }

  16.     root->len ++;

  17.     _rb_tree_insert_fixup(root,node);

  18.     return 0;
  19. }
查找代码为:
  1. int rb_tree_insert(struct rb_root *root,struct rb_node *node)
  2. {
  3.     struct rb_node *p;
  4.         
  5.     _rb_tree_find(root,node,&p);
  6.     
  7.     if(p->key < node->key)
  8.     {
  9.      p->right = node;
  10.      node->parent = p;
  11.     }
  12.     else {
  13.      p->left = node;
  14.      node->parent = p;
  15.     }

  16.     root->len ++;

  17.     _rb_tree_insert_fixup(root,node);

  18.     return 0;
  19. }
其中,最复杂的为颜色调整部分了,如下:
  1. static void _rb_tree_insert_fixup(struct rb_root *root,struct rb_node *p)
  2. {
  3.     struct rb_node *q;

  4.     while(p && p->parent && p->parent->color == RED)
  5.     {
  6.      
  7.     if(p->parent->parent && p->parent == p->parent->parent->left)    
  8.      {
  9.         q = p->parent->parent->right;
  10.         if(q && q->color == RED)
  11.         {
  12.          p->parent->color = BLACK;
  13.          p->parent->parent->color = RED;
  14.          q->color = BLACK;
  15.          p = p->parent->parent;
  16.          continue;
  17.         }

  18.         if(p->parent->right && p->parent->right == p)
  19.          {
  20.          p = p->parent;
  21.          left_rotate(root,p);
  22.          }
  23.         
  24.         if(p && p->parent)
  25.         p->parent->color = BLACK;
  26.         if(p && p->parent && p->parent->parent)
  27.         {
  28.          p->parent->parent->color = RED;
  29.          right_rotate(root,p->parent->parent);
  30.         }            
  31.      }
  32.     else
  33.     {    
  34.         if(p->parent->parent && p->parent->parent->left)
  35.         {
  36.          q = p->parent->parent->left;
  37.          if(q && q->color == RED)
  38.          {
  39.             p->parent->parent->color = RED;
  40.             p->parent->color = BLACK;
  41.             q->color = BLACK;
  42.             p = p->parent->parent;
  43.             continue;
  44.          }
  45.         }

  46.         if(p->parent->left && p->parent->left == p)
  47.         {
  48.             p = p->parent;
  49.             right_rotate(root,p);
  50.         }
  51.     
  52.         if(p && p->parent)
  53.         p->parent->color = BLACK;
  54.         if(p && p->parent && p->parent->parent)
  55.         {
  56.             p->parent->parent->color = RED;
  57.             left_rotate(root,p->parent->parent);
  58.         }
  59.     }    
  60.     }

  61.     root->root->color = BLACK;
  62.     
  63. }

删除节点

这段代码基本来自Linux内核(lib/rb_tree.c)中,进行了少量的修改
  1. /*
  2. *from linux kernel
  3. */
  4. int rb_tree_erase(struct rb_root *root,struct rb_node *node)
  5. {
  6.     struct rb_node *child,*parent;
  7.     int color;
  8.     
  9.     if(!node->left)    
  10.         child = node->right;
  11.     else if(!node->right)    
  12.         child = node->left;
  13.     else
  14.     {
  15.         struct rb_node *old = node,*left;

  16.         node = node->right;
  17.         while((left = node->left) != NULL)
  18.             node = left;
  19.         child = node->right;
  20.         parent = node->parent;
  21.         color = node->color;
  22.         
  23.         if(child) child->parent = parent;
  24.         if(parent == old) {
  25.             parent->right = child;
  26.             parent = node;
  27.         } else
  28.             parent->left = child;
  29.         
  30.         node->parent = old->parent;
  31.         node->color = old->color;
  32.         node->right = old->right;
  33.         node->left = old->left;
  34.         
  35.         if(old->parent)
  36.         {
  37.             if(old->parent->left == old)
  38.                 old->parent->left = node;
  39.             else    old->parent->right = node;
  40.         } else
  41.             root->root = node;
  42.         
  43.         old->left->parent = node;
  44.         if(old->right)
  45.             old->right->parent = node;
  46.         goto color;
  47.     }
  48.     parent = node->parent;
  49.     color = node->color;

  50.     if(child)
  51.         child->parent = parent;
  52.     if(parent)
  53.     {
  54.         if(parent->left == node)
  55.             parent->left = child;
  56.         else     parent->right = child;
  57.     } else
  58.         root->root = child;
  59. color:
  60.     if(color == BLACK)
  61.         __rb_tree_erase_fixup(root,parent,child);

  62.     root->len --;
  63.     
  64.     return 0;
  65. }
接着又是调整颜色的代码:
  1. void __rb_tree_erase_fixup(struct rb_root *root,struct rb_node *parent,\
  2.                 struct rb_node *x)
  3. {
  4.     struct rb_node *w;

  5.     while( x != root->root && (!x || x->color==BLACK))
  6.     {
  7.         if( x == parent->left)
  8.         {
  9.             w = parent->right;
  10.             //case 1
  11.             if(w->color == RED)    
  12.             {
  13.                 w->color = BLACK;
  14.                 parent->color = RED;
  15.                 left_rotate(root,parent);
  16.                 w = parent->right;
  17.             }
  18.             //case 2
  19.             if((!w->left || w->left->color == BLACK) && \
  20.                 (!w->right || w->right->color==BLACK))
  21.             {
  22.                 w->color = RED;
  23.                 x = parent;
  24.                 parent = x->parent;
  25.             }
  26.             // case 3
  27.             else
  28.             {
  29.             if( !w->right || w->right->color == BLACK)
  30.             {
  31.                 w->color = RED;
  32.                 if(w->left)
  33.                     w->left->color = BLACK;
  34.                 right_rotate(root,w);
  35.                 w = parent->right;
  36.             }
  37.                 
  38.             //case 4
  39.             w->color = parent->color;
  40.             if(w->right)
  41.                 w->right->color = BLACK;
  42.             parent->color = BLACK;
  43.             left_rotate(root,parent);
  44.             x = root->root;
  45.             break;
  46.             }
  47.             
  48.         }
  49.         else//same as if ,left<-->right
  50.         {
  51.             w = parent->left;
  52.             //case 1
  53.             if(RED == w->color)
  54.             {
  55.                 w->color = BLACK;
  56.                 parent->color = RED;    
  57.                 right_rotate(root,parent);
  58.                 w = parent->left;
  59.             }
  60.             //case 2
  61.             if((!w->right || w->right->color == BLACK) && \
  62.                 (!w->left || w->left->color == BLACK))
  63.             {
  64.                 w->color = RED;
  65.                 x = parent;
  66.                 parent = x->parent;
  67.             }
  68.             else
  69.             {
  70.             if(!w->left || w->left->color == BLACK)
  71.             {
  72.                 w->color = RED;
  73.                 if(w->right)
  74.                     w->right->color = BLACK;
  75.                 left_rotate(root,w);
  76.                 w = parent->left;
  77.             }    
  78.             //case 4
  79.             w->color = parent->color;
  80.             if(w->left)
  81.                 w->left->color = BLACK;
  82.             parent->color = BLACK;
  83.             right_rotate(root,parent);
  84.             x = root->root;
  85.             break;
  86.             }
  87.         }
  88.     }
  89.     if(x)
  90.     x->color = BLACK;
  91. }
PS:删除部分,本来是将书上的伪码实现,最后发现老是编译段错误,最后就直接修改linux内核中,哎!
参考资料
1.算法导论(影印版)
2.linux-2.6.24.3内核源码
3.
阅读(1379) | 评论(0) | 转发(1) |
给主人留下些什么吧!~~