The Algorithms logo
The Algorithms
AboutDonate
/* demo.c -- Implementations of multikey quicksort and ternary search trees
   Usage
    demo                  Run basic timings on /usr/dict/words
    demo <file>           Run basic timings on <file>
    demo <file> trysearch Interactive pm and nn search on <file>
    demo <file> nncost    Run near neigbhor expers on <file>
    demo <file> pmcost    Interactive partial match expers on <file>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

// MULTIKEY QUICKSORT

#ifndef min
#define min(a, b) ((a) <= (b) ? (a) : (b))
#endif

#define swap(a, b)      \
    {                   \
        char *t = x[a]; \
        x[a] = x[b];    \
        x[b] = t;       \
    }
#define i2c(i) x[i][depth]

void vecswap(int i, int j, int n, char *x[])
{
    while (n-- > 0)
    {
        swap(i, j);
        i++;
        j++;
    }
}

void ssort1(char *x[], int n, int depth)
{
    int a, b, c, d, r, v;
    if (n <= 1)
        return;
    a = rand() % n;
    swap(0, a);
    v = i2c(0);
    a = b = 1;
    c = d = n - 1;
    for (;;)
    {
        while (b <= c && (r = i2c(b) - v) <= 0)
        {
            if (r == 0)
            {
                swap(a, b);
                a++;
            }
            b++;
        }
        while (b <= c && (r = i2c(c) - v) >= 0)
        {
            if (r == 0)
            {
                swap(c, d);
                d--;
            }
            c--;
        }
        if (b > c)
            break;
        swap(b, c);
        b++;
        c--;
    }
    r = min(a, b - a);
    vecswap(0, b - r, r, x);
    r = min(d - c, n - d - 1);
    vecswap(b, n - r, r, x);
    r = b - a;
    ssort1(x, r, depth);
    if (i2c(r) != 0)
        ssort1(x + r, a + n - d - 1, depth + 1);
    r = d - c;
    ssort1(x + n - r, r, depth);
}

void ssort1main(char *x[], int n) { ssort1(x, n, 0); }

// ssort2 -- Faster Version of Multikey Quicksort

void vecswap2(char **a, char **b, int n)
{
    while (n-- > 0)
    {
        char *t = *a;
        *a++ = *b;
        *b++ = t;
    }
}

#define swap2(a, b)  \
    {                \
        t = *(a);    \
        *(a) = *(b); \
        *(b) = t;    \
    }
#define ptr2char(i) (*(*(i) + depth))

char **med3func(char **a, char **b, char **c, int depth)
{
    int va, vb, vc;
    if ((va = ptr2char(a)) == (vb = ptr2char(b)))
        return a;
    if ((vc = ptr2char(c)) == va || vc == vb)
        return c;
    return va < vb ? (vb < vc ? b : (va < vc ? c : a))
                   : (vb > vc ? b : (va < vc ? a : c));
}
#define med3(a, b, c) med3func(a, b, c, depth)

void inssort(char **a, int n, int d)
{
    char **pi, **pj, *s, *t;
    for (pi = a + 1; --n > 0; pi++)
        for (pj = pi; pj > a; pj--)
        {
            // Inline strcmp: break if *(pj-1) <= *pj
            for (s = *(pj - 1) + d, t = *pj + d; *s == *t && *s != 0; s++, t++)
                ;
            if (*s <= *t)
                break;
            swap2(pj, pj - 1);
        }
}

void ssort2(char **a, int n, int depth)
{
    int d, r, partval;
    char **pa, **pb, **pc, **pd, **pl, **pm, **pn, *t;
    if (n < 10)
    {
        inssort(a, n, depth);
        return;
    }
    pl = a;
    pm = a + (n / 2);
    pn = a + (n - 1);
    if (n > 30)
    {  // On big arrays, pseudomedian of 9
        d = (n / 8);
        pl = med3(pl, pl + d, pl + 2 * d);
        pm = med3(pm - d, pm, pm + d);
        pn = med3(pn - 2 * d, pn - d, pn);
    }
    pm = med3(pl, pm, pn);
    swap2(a, pm);
    partval = ptr2char(a);
    pa = pb = a + 1;
    pc = pd = a + n - 1;
    for (;;)
    {
        while (pb <= pc && (r = ptr2char(pb) - partval) <= 0)
        {
            if (r == 0)
            {
                swap2(pa, pb);
                pa++;
            }
            pb++;
        }
        while (pb <= pc && (r = ptr2char(pc) - partval) >= 0)
        {
            if (r == 0)
            {
                swap2(pc, pd);
                pd--;
            }
            pc--;
        }
        if (pb > pc)
            break;
        swap2(pb, pc);
        pb++;
        pc--;
    }
    pn = a + n;
    r = min(pa - a, pb - pa);
    vecswap2(a, pb - r, r);
    r = min(pd - pc, pn - pd - 1);
    vecswap2(pb, pn - r, r);
    if ((r = pb - pa) > 1)
        ssort2(a, r, depth);
    if (ptr2char(a + r) != 0)
        ssort2(a + r, pa - a + pn - pd - 1, depth + 1);
    if ((r = pd - pc) > 1)
        ssort2(a + n - r, r, depth);
}

void ssort2main(char **a, int n) { ssort2(a, n, 0); }

// TERNARY SEARCH TREE ALGS

typedef struct tnode *Tptr;
typedef struct tnode
{
    char splitchar;
    Tptr lokid, eqkid, hikid;
} Tnode;
Tptr root;

// Insert 1 -- Simple Insertion Algorithm

Tptr insert1(Tptr p, char *s)
{
    if (p == 0)
    {
        p = (Tptr)malloc(sizeof(Tnode));
        p->splitchar = *s;
        p->lokid = p->eqkid = p->hikid = 0;
    }
    if (*s < p->splitchar)
        p->lokid = insert1(p->lokid, s);
    else if (*s == p->splitchar)
    {
        if (*s != 0)
            p->eqkid = insert1(p->eqkid, ++s);
    }
    else
        p->hikid = insert1(p->hikid, s);
    return p;
}

void cleanup1(Tptr p)
{
    if (p)
    {
        cleanup1(p->lokid);
        cleanup1(p->eqkid);
        cleanup1(p->hikid);
        free(p);
    }
}

// Insert 2 -- Faster version of Insert

#define BUFSIZE 1000
Tptr buffer;
int bufn, freen;
void *freearr[10000];
int storestring = 0;

void insert2(char *s)
{
    int d;
    char *instr = s;

    Tptr pp, *p;
    p = &root;
    pp = *p;
    while (pp == *p)
    {
        if ((d = *s - pp->splitchar) == 0)
        {
            if (*s++ == 0)
                return;
            p = &(pp->eqkid);
        }
        else if (d < 0)
            p = &(pp->lokid);
        else
            p = &(pp->hikid);
    }
    for (;;)
    {
        // *p = (Tptr) malloc(sizeof(Tnode));
        if (bufn-- == 0)
        {
            buffer = (Tptr)malloc(BUFSIZE * sizeof(Tnode));
            freearr[freen++] = (void *)buffer;
            bufn = BUFSIZE - 1;
        }
        *p = buffer++;
        pp = *p;
        pp->splitchar = *s;
        pp->lokid = pp->eqkid = pp->hikid = 0;
        if (*s++ == 0)
        {
            if (storestring)
                pp->eqkid = (Tptr)instr;
            return;
        }
        p = &(pp->eqkid);
    }
}
void cleanup2()
{
    int i;
    for (i = 0; i < freen; i++) free(freearr[i]);
}

// Search Algorithms

int search1(char *s)
{
    Tptr p;
    p = root;
    while (p)
    {
        if (*s < p->splitchar)
            p = p->lokid;
        else if (*s == p->splitchar)
        {
            if (*s++ == 0)
                return 1;
            p = p->eqkid;
        }
        else
            p = p->hikid;
    }
    return 0;
}

int search2(char *s)
{
    int d, sc;
    Tptr p;
    sc = *s;
    p = root;
    while (p)
    {
        if ((d = sc - p->splitchar) == 0)
        {
            if (sc == 0)
                return 1;
            sc = *++s;
            p = p->eqkid;
        }
        else if (d < 0)
            p = p->lokid;
        else
            p = p->hikid;
    }
    return 0;
}

// Advanced searching: Partial match, near words

int nodecnt;
char *srcharr[100000];
int srchtop;

void pmsearch(Tptr p, char *s)
{
    if (!p)
        return;
    nodecnt++;
    if (*s == '.' || *s < p->splitchar)
        pmsearch(p->lokid, s);
    if (*s == '.' || *s == p->splitchar)
        if (p->splitchar && *s)
            pmsearch(p->eqkid, s + 1);
    if (*s == 0 && p->splitchar == 0)
        srcharr[srchtop++] = (char *)p->eqkid;
    if (*s == '.' || *s > p->splitchar)
        pmsearch(p->hikid, s);
}

void nearsearch(Tptr p, char *s, int d)
{
    if (!p || d < 0)
        return;
    nodecnt++;
    if (d > 0 || *s < p->splitchar)
        nearsearch(p->lokid, s, d);
    if (p->splitchar == 0)
    {
        if ((int)strlen(s) <= d)
            srcharr[srchtop++] = (char *)p->eqkid;
    }
    else
        nearsearch(p->eqkid, *s ? s + 1 : s, (*s == p->splitchar) ? d : d - 1);
    if (d > 0 || *s > p->splitchar)
        nearsearch(p->hikid, s, d);
}

#define NUMBER_OF_STRING 3

int main(int argc, char *argv[])
{
    char *arr[NUMBER_OF_STRING] = {"apple", "cat", "boy"};

    ssort1main(arr, NUMBER_OF_STRING);

    for (int i = 0; i < NUMBER_OF_STRING; i++)
    {
        printf("%s ", arr[i]);
    }
}

Multikey Quick Sort

K