Algorithm: cartesian tree

http://baike.baidu.com/link?url=XUt5fXQ-jtFBM0UdKiGA41_NWFvdFSYwVsy4SVvCRRuEBvNkLfT9TgOtzsXvaOT9nuq_EzKJcO0gt6nyXRSLU_

这里有详细介绍

有一道coding test的题目给你一个int n，一串float的数，要你实时打印出当前数到这个数前n个数这n个数里最大值，没有n个数就是前面那几个数的最大值。这里就可以用cartesian tree，label记录是数的下标，p表示数值。插入操作为lg(n), 删除操作也为lg(n)，总的复杂度为Nlg(n).

  1 #include <iostream>
  2 #include <fstream>
  3 #include <cstdio>
  4 
  5 using namespace std;
  6 
  7 class treap_node 
  8 {
  9     public:
 10         int label;
 11         float p;
 12         treap_node *left;
 13         treap_node *right;
 14         treap_node()
 15         {
 16             left = NULL;
 17             right = NULL;
 18         }
 19 };
 20 
 21 class treap:treap_node
 22 {
 23     public:
 24         treap_node *root;
 25         treap()
 26         {
 27             root = NULL;
 28         }
 29         void treap_left_rotate(treap_node* &a)
 30         {
 31             treap_node *b = a->right;
 32             a->right = b->left;
 33             b->left = a;
 34             a = b;
 35         }
 36         void treap_right_rotate(treap_node* &a)
 37         {
 38             treap_node *b = a->left;
 39             a->left = b->right;
 40             b->right = a;
 41             a = b;
 42         }
 43         void treap_insert(treap_node* &a, int &label, float &p)
 44         {
 45             if (!a)
 46             {
 47                 a = new treap_node;
 48                 a->label = label;
 49                 a->p = p;
 50             }
 51             else if (label > a->label)
 52             {
 53                 treap_insert(a->right, label, p);
 54                 if (a->right->p > a->p)
 55                     treap_left_rotate(a);
 56             }
 57             else
 58             {
 59                 treap_insert(a->left, label, p);
 60                 if (a->left->p < a->p)
 61                     treap_right_rotate(a);
 62             }
 63         }
 64         void treap_delete_smallestP(treap_node* &a)
 65         {
 66             treap_node *p = a;
 67             treap_node *pre = NULL;
 68             while (p->left != NULL)
 69             {
 70                 pre = p;
 71                 p = p->left;
 72             }
 73             if (pre != NULL)
 74             {
 75                 pre->left = p->right;
 76             }
 77             else
 78                 a = p->right;
 79             return;
 80         }
 81         void plist(treap_node *a) 
 82         {
 83             if (a != NULL)
 84             {
 85                 cout << "(";
 86                 plist(a->left);
 87                 cout << a->label << "/" << a->p;
 88                 plist(a->right);
 89                 cout << ")";
 90             }
 91         }
 92 };
 93 
 94 int atoi(char *s) 
 95 {
 96     int ret = 0;
 97     while (*s != '\0') {
 98         ret = ret * 10 + (int)(*s - '0');
 99         s++;
100     }
101     return ret;
102 }
103 
104 int main(int argc, char **argv) 
105 {
106  if (argc != 3) {
107      cout << "invalid input" << endl;
108    return 1;
109  }
110  //cout << argv[1] << " " << argv[2] << endl;
111  ifstream fin(argv[2]);
112  if (!fin) {
113      cout << "unable to open the file" << endl;
114      return 1;
115  }
116  int n = atoi(argv[1]);
117  int count = 0;
118  treap *p = new treap;
119  float s;
120  while (fin >> s) {
121      cout << s << " ";
122      if (count >= n) 
123      {
124          p->treap_delete_smallestP(p->root);
125      }
126      p->treap_insert(p->root, count, s);
127      p->plist(p->root); 
128      cout << p->root->p << endl;
129      count++;
130  }
131  return 0;
132 }

posted @ 2013-10-02 18:19 ying_vincent 阅读(296) 评论(0) 收藏举报

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