开放定址法解决hash冲突(C语言)

/* * hashquad.c 开放定址法解决hash冲突问题 */ #include <stdio.h> #include <stdlib.h> #include "hashquad.h" #include "fatal.h" #define MIN_TABLE_SIZE (10) #define REHASH_FACTOR (0.7) enum kind_of_entry { legitimate, empty, deleted }; struct hash_entry { element_type element; enum kind_of_entry info; }; typedef struct hash_entry cell; struct hash_tbl { int table_size; /* 表容量 */ int entry_cnt; /* 已填入的单元数量 */ cell *cells; }; static int need_rehash( hash_table h ) { return ( h->entry_cnt > h->table_size * REHASH_FACTOR ); } static int next_prime( int N ) { int i; if ( N % 2 == 0 ) N++; for ( ; ; N += 2 ){ for ( i = 3; i * i <= N; i += 2 ){ if ( N % i == 0 ) goto cont_outer; } return N; cont_outer: ; } } static Index hash( element_type key, int table_size ) { return key % table_size; } static hash_table initialize_table( int table_size ) { hash_table h; int i; if ( table_size < MIN_TABLE_SIZE ) Error("Table size too small!"); h = malloc( sizeof( struct hash_tbl ) ); if ( h == NULL ) Error("Out of space!"); h->table_size = next_prime( table_size ); h->cells = malloc( sizeof( cell ) * h->table_size ); if ( h->cells == NULL ){ free( h ); Error("Out of space!"); } for ( i = 0; i < h->table_size; i++){ h->cells[ i ].info = empty; } h->entry_cnt = 0; return h; } static Pos find( element_type key, hash_table h ) { Pos cur_pos; int collision_num; collision_num = 0; cur_pos = hash( key, h->table_size ); /* 当hash表大部分被占满，这个过程可能很慢。 也有可能进入死循环! 需要在适当的时候进行rehash! */ while ( h->cells[ cur_pos ].info != empty && h->cells[ cur_pos ].element != key ){ cur_pos += 2 * ++collision_num - 1; if ( cur_pos >= h->table_size ) cur_pos -= h->table_size; } return cur_pos; } static void insert( element_type key, hash_table h ) { Pos p; p = find( key, h ); if ( h->cells[ p ].info != legitimate ){ h->cells[ p ].info = legitimate; h->cells[ p ].element = key; h->entry_cnt++; } } static hash_table rehash( hash_table h) { int i, old_size; cell *old_cells; old_cells = h->cells; old_size = h->table_size; /* 创建一个新的double size的空表 */ h = initialize_table( 2 * old_size ); /* 拷贝旧表的数据到新表 */ for ( i = 0; i < old_size; i++ ){ if ( old_cells[ i ].info == legitimate ) insert( old_cells[ i ].element, h ); } free( old_cells ); return h; } /************ The next is test functions ***************/ #define get_array_size(array) ( sizeof(array) / sizeof(array[0]) ) void test_hashquad( void ) { int i; Pos p; hash_table h; element_type datas[100]; for ( i = 0; i < get_array_size( datas ); i++ ){ datas[i] = rand() % 1000; } h = initialize_table( 13 ); if ( h == NULL ) Error("Initialize error!"); for ( i = 0; i < get_array_size( datas ); i++ ){ insert( datas[i], h ); /* 在每次插入操作后检查是否需要rehash */ if ( need_rehash( h ) ) h = rehash( h ); } p = find( 67, h ); if ( h->cells[p].info != legitimate ){ printf("/n/t key value 67 not in hash table!/n"); }else{ printf("/n/t key value 67 in hash table!/n"); } p = find( datas[31], h ); if ( h->cells[p].info != legitimate ){ printf("/n/t key value %d not in hash table!/n",datas[31]); }else{ printf("/n/t key value %d in hash table!/n",datas[31]); } i = i; return; } /*********************************************************************************************************/ /* hashquad.h */ #ifndef _HASHQUAD_H_ #define _HASHQUAD_H_ typedef int element_type; typedef unsigned int Index; typedef Index Pos; struct hash_tbl; typedef struct hash_tbl *hash_table; #endif