高级数据结构-SkipList

 SkipList     

       

代码：

 

//skiplist: A probabilistic alternative balanced tree#include <stdlib.h>#include <stdio.h>#include <limits.h>#include <string.h>#define MaxLevel 7struct  SkipNode{int value;struct SkipNode** forward;};struct SkipList{int level;int size;struct SkipNode *head;};struct SkipList* init(struct SkipList* List){struct SkipNode *Head = (struct SkipNode*)malloc(sizeof(struct SkipNode));List->head = Head;Head->value = INT_MAX;Head->forward = (struct SkipNode**)malloc(sizeof(struct SkipNode*) * (MaxLevel+1));int i = 0;for( i = 0; i<= MaxLevel; i++)Head->forward[i] = List->head;List->level = 1;List->size = 0;return List;}static int randLevel(){int level = 1;while( (rand()%10) <5 && level < MaxLevel)level++;return level;}void sInsert(struct SkipList* List, int key){struct SkipNode *update[MaxLevel+1];struct SkipNode* p = List->head;int i;for( i = List->level; i>= 1 ; i--){while( p->forward[i]->value < key)p = p->forward[i];update[i] = p;}   // 找到各层不大于 key 的指针p = p->forward[1];if( key == p->value)return;int level = randLevel();//printf("%d ", level);if( level > List->level){for( i = List->level+1; i <= level; i++)update[i] = List->head;List->level = level;}++List->size;struct SkipNode* x= (struct SkipNode* )malloc(sizeof(struct SkipNode));x->value = key;x->forward = (struct SkipNode**)malloc(sizeof(struct SkipNode*) * (level+1));for(i = 1; i<= level; i++){x->forward[i] = update[i]->forward[i];update[i]->forward[i] = x;}}struct SkipNode* sFind(struct SkipList* List, int key){struct SkipNode* p = List->head;int i;for( i = List->level ; i>= 1; i--){while(p->forward[i]->value < key)p = p->forward[i];}if( p->forward[1]->value == key)return p->forward[1];elsereturn NULL;}void sDelete(struct SkipList* List, int key){struct SkipNode* update[MaxLevel+1];struct SkipNode* p = List->head;int i;for(i = List->level; i>=1; i--){while( p->forward[i]->value < key)p= p->forward[i];update[i] = p;}p = p->forward[1];if( p->value != key)return ;else{for(i = 1; i<= List->level; i++){if(update[i]->forward[i] != p)break;update[i]->forward[i] = p->forward[i];}free(p->forward);free(p);--List->size;while(List->level >1 && (List->head->forward[List->level] == List->head))--List->level;}}//for testint main(int argc, char** argv){struct SkipList  List;init(&List);int array[] = {3,6,9,2,11,1,4};int i;for(i =0; i < 7; i++)sInsert(&List, array[i]);sDelete(&List, 4);printf("%d\n", List.size);struct SkipNode *q = sFind(&List, 11);printf("%d\n", q->value);printf("Hello World\n");return 0;}