Organize Your Train part II(hash)

http://poj.org/problem?id=3007

第一次用STL做的，TLE了，自己构造字符串哈希函数才可以。。

TLE代码：

 

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <string>
#include <map>
using namespace std;
int main()
{
    int n;
    scanf("%d",&n);
    while(n--)
    {
        int cnt = 0,j;
        char ss[120];
        string str,s,s1,s2;
        map<string,int>v;
        cin>>str;
        s = str;
        int len = str.size();

        for (int i = 1; i < len; i++)
        {
            s = str;
            string::iterator it = s.begin();
            for (j = 0; j < i; j++)
                ss[j] = str[j];
            ss[j] = '';
            s1 = ss;
            s.erase(it,it+i);
            s2 = s;
            for (int k = 1; k <= 4; k++)
            {
                if (v[s1+s2]==0)
                {
                    v[s1+s2]++;
                    cnt++;
                }
                if (v[s2+s1]==0)
                {
                    v[s2+s1]++;
                    cnt++;
                }
                if (k==1)
                    reverse(s1.begin(),s1.end());
                else if (k==2)
                    reverse(s2.begin(),s2.end());
                else if (k==3)
                    reverse(s1.begin(),s1.end());
            }
        }
        printf("%d
",cnt);
    }
    return 0;
}

AC代码：

 

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
const int N=100000;
const int MOD=9467;
int cnt = 0;

struct node
{
    char s[120];
    struct node *next;
}*hash[N];

void Hash(char *s1,char *s2)
{
    char ss[120],*str;
    strcpy(ss,s1);
    strcat(ss,s2);
    str = ss;
    unsigned int key = 0;
    while(*str)
    {
        key = key*131+(*str++);
    }
    key%=99991;
    if (!hash[key])
    {
        hash[key] = new node;
        strcpy(hash[key]->s,ss);
        hash[key]->next = NULL;
        cnt++;
    }
    else
    {
        struct node *p = hash[key];
        if(strcmp(p->s,ss)==0)
            return ;
        while(p->next)
        {
            if (!strcmp(p->next->s,ss))
                return ;
            p = p->next;
        }
        p->next = new node;
        strcpy(p->next->s,ss);
        p->next->next = NULL;
        cnt++;
    }
}
int main()
{

    char s[120],s1[120],s2[120],s3[120],s4[120];
    int n,j;
    scanf("%d",&n);
    while(n--)
    {
        cnt = 0;
        scanf("%s",s);
        int len = strlen(s);
        memset(hash,0,sizeof(hash));
        for (int i = 1; i < len; i++)
        {
            for (j = 0; j < i; j++)
                s1[j] = s[j];
            s1[j] = '';
            for (j = i; j < len; j++)
                s2[j-i] = s[j];
            s2[j-i] = '';
            strcpy(s3,s1);
            strcpy(s4,s2);
            reverse(s1,s1+i);
            reverse(s2,s2+len-i);
            Hash(s3,s4);
            Hash(s4,s3);
            Hash(s1,s4);
            Hash(s4,s1);
            Hash(s2,s3);
            Hash(s3,s2);
            Hash(s1,s2);
            Hash(s2,s1);

        }
        printf("%d
",cnt);
    }
    return 0;
}

有关字符串哈希函数的经典算法

 

unsigned int SDBMHash(char *str)
{
    unsigned int hash = 0;
 
    while (*str)
    {
        // equivalent to: hash = 65599*hash + (*str++);
        hash = (*str++) + (hash << 6) + (hash << 16) - hash;
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// RS Hash Function
unsigned int RSHash(char *str)
{
    unsigned int b = 378551;
    unsigned int a = 63689;
    unsigned int hash = 0;
 
    while (*str)
    {
        hash = hash * a + (*str++);
        a *= b;
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// JS Hash Function
unsigned int JSHash(char *str)
{
    unsigned int hash = 1315423911;
 
    while (*str)
    {
        hash ^= ((hash << 5) + (*str++) + (hash >> 2));
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// P. J. Weinberger Hash Function
unsigned int PJWHash(char *str)
{
    unsigned int BitsInUnignedInt = (unsigned int)(sizeof(unsigned int) * 8);
    unsigned int ThreeQuarters    = (unsigned int)((BitsInUnignedInt  * 3) / 4);
    unsigned int OneEighth        = (unsigned int)(BitsInUnignedInt / 8);
    unsigned int HighBits         = (unsigned int)(0xFFFFFFFF) << (BitsInUnignedInt - OneEighth);
    unsigned int hash             = 0;
    unsigned int test             = 0;
 
    while (*str)
    {
        hash = (hash << OneEighth) + (*str++);
        if ((test = hash & HighBits) != 0)
        {
            hash = ((hash ^ (test >> ThreeQuarters)) & (~HighBits));
        }
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// ELF Hash Function
unsigned int ELFHash(char *str)
{
    unsigned int hash = 0;
    unsigned int x    = 0;
 
    while (*str)
    {
        hash = (hash << 4) + (*str++);
        if ((x = hash & 0xF0000000L) != 0)
        {
            hash ^= (x >> 24);
            hash &= ~x;
        }
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// BKDR Hash Function
unsigned int BKDRHash(char *str)
{
    unsigned int seed = 131; // 31 131 1313 13131 131313 etc..
    unsigned int hash = 0;
 
    while (*str)
    {
        hash = hash * seed + (*str++);
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// DJB Hash Function
unsigned int DJBHash(char *str)
{
    unsigned int hash = 5381;
 
    while (*str)
    {
        hash += (hash << 5) + (*str++);
    }
 
    return (hash & 0x7FFFFFFF);
}
 
// AP Hash Function
unsigned int APHash(char *str)
{
    unsigned int hash = 0;
    int i;
 
    for (i=0; *str; i++)
    {
        if ((i & 1) == 0)
        {
            hash ^= ((hash << 7) ^ (*str++) ^ (hash >> 3));
        }
        else
        {
            hash ^= (~((hash << 11) ^ (*str++) ^ (hash >> 5)));
        }
    }
 
    return (hash & 0x7FFFFFFF);
}