完美散列函数（一）

// cxy1.cpp : Defines the entry point for the console application.//#include "stdafx.h"/*--- birthday.c --------------------------- Listing 3-1 -------- * Reads input file of birthdays and lists any duplicates. * Uses a simple hash table to identify the duplicates. * * Input records consists of lines of text of the form * MMDDName where MM = month, DD = day, Name. For example: *                  0212Abraham Lincoln * Note: for simplicity, no error checking is done on records. *-------------------------------------------------------------*/#include <stdio.h>#include <stdlib.h>#include <string.h>#define TABLE_SIZE 366  /* Maximum days in a year */FILE *fin;              /* Birthday file */int  NameCount,         /* Number of names read */     DupeCount;         /* Number of dupes found */int hash_birthday ( char * );   /* Our hash function */#ifdef __STDC__         /* in ANSI C, there's no strdup() *//* the source code for this function is discussed in Ch. 2 */char *strdup ( const char * );  /* string duplication */#endifint main (  ){    char buffer[128];   /* where the records will be read */    int  hash_value;    /* the hash value we will compute */    char *name;         /* pointer to birthday name       */    char *Table[TABLE_SIZE];   /* table of birthday folks */    int i;              /* subscript to init the table    */    if (( fin = fopen ( "rt.txt", "rt" )) == NULL )    {               exit ( EXIT_FAILURE );    }    for ( i = 0; i < TABLE_SIZE; i++ )          Table[i] = NULL;    while ( ! feof ( fin ))    {        if ( fgets ( buffer, 128, fin ) == NULL )            break;        /* get rid of the '\n' at end of record */        buffer [strlen ( buffer ) - 1] = '\0';        NameCount += 1;        hash_value = hash_birthday ( buffer );        name = strdup ( buffer + 4 );        if ( Table[hash_value] == NULL )  /* No duplicate, */        {                                 /* so add name.  */            Table[hash_value] = name;            continue;        }        else        {                                 /* Is duplicate, */            DupeCount += 1;               /* so tell 'em.  */            printf ( "%s and %s have the same birthday.\n",                    name, Table[hash_value] );            continue;        }    }    if ( DupeCount == 0 )    {        printf ( "No duplicate matches found among %d people.\n",                  NameCount );        if ( NameCount > 50 )            printf ( "How rare!\n" );    }    else        printf ( "Among %d people, %d matches were found\n",                NameCount, DupeCount );    return ( EXIT_SUCCESS );}/*--------------------------------------------------------------- * A simple hash algorithm. It converts the month and day * to the number of the day in the year. Adds the day in the * month to the number of days elapsed before that month began. *-------------------------------------------------------------*/int hash_birthday ( char *data ){    const int days_elapsed[12] =      { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 };    int mm, dd;    char record [128];  /* where we store our copy of the data */    strcpy ( record, data );  /* make our own copy */    record [4] = '\0';  /* Mark the spot where the name begins */    dd = atoi ( record + 2 );   /* Convert the day to an int */    record [2] = '\0';  /* Mark off the spot where day begins */    mm = atoi ( record );       /* Convert the month to an int */    /* since mm is going to be an index into days_elapsed,     * it must be checked for the correct range.     */    if ( mm < 1 || mm > 12 )    {        fprintf ( stderr, "Error in record for %s: %02d/%02d\n",                 (char *) data + 4, mm, dd );        exit ( EXIT_FAILURE );    }    return ( days_elapsed[mm - 1] + dd );}

查询生日同一天的代码

1017My sister0212Abraham Lincoln0704USA0707Ringo Starr0214St Valentine0531Johnstown Flood of 18890725Andrea Doria sinks 19560728Plane hits Empire State Bldg 19450902Great Fire of London begins 16660911Hurricane Iniki 19921017San Francisco Quake 19890327My brother