StringPatternAlgorithmsTesting/ssm.h at master · DeDTihoN/StringPatternAlgorithmsTesting · GitHub

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//
// Created by pc on 5/31/2024.
//

#ifndef ESTIMATINGSTRINGPATTERNALGORITHMS_SSM_H
#define ESTIMATINGSTRINGPATTERNALGORITHMS_SSM_H

#include "include/define.h"
#include "include/main_header.h"
#include "Algorithm.h"

class ssm : public Algorithm {
public:
    const char *name() const override {
        return "SSM";
    }

    void Horspool_Distance(int Horspool[], int Dist[], unsigned char *x, int m, int *dMax) {
        int i;
        Dist[m] = 0;
        for (i = 0; i < SIGMA; i++) Horspool[i] = m;
        for (i = 0; i < m - 1; i++) {
            if (Horspool[x[i]] == m)
                Dist[i] = i + 1;
            else
                Dist[i] = i - (m - Horspool[x[i]] - 1);
            Horspool[x[i]] = m - i - 1;
            if (Dist[i] > Dist[m]) {
                Dist[m] = Dist[i];
                *dMax = i;
            }
        }
    }

//************************************************************************//
    void PreProc(int Dist[], int Shift[], unsigned char *x, int m) {
        /*----compute the safe shift from left to right*/
        int i, rept = 1;
        Shift[0] = 1;
        for (i = 1; i < m; i++) {
            if (x[i] != x[i - 1]) {
                Shift[i] = 1;
                rept = 1;
            } else {
                rept++;
                Shift[i] = rept;
            }
        }

        /*----compute the safe shift from right to left*/
        rept = 1;
        for (i = m - 1; i > 0; i--) {
            if (x[i] != x[i - 1]) {
                if (rept >= Shift[i - 1])
                    Shift[i - 1] = rept + 1;
                rept = 1;
            } else
                rept++;
        }

        /*----Compute the max shift of all shifts----*/

        for (i = 0; i < m; i++)
            if (Shift[i] < Dist[m])
                Shift[i] = Dist[m];
    }

/*-------------------------------------------------------------*/
    int search(unsigned char *x, int m, unsigned char *y, int n) override {

        int count, q, j, Max, jMax, Pos;
        int Hors[SIGMA], Sht[XSIZE], Dis[XSIZE];
        unsigned char xMax;

        /*Preprocessing phase-----------*/
        Horspool_Distance(Hors, Dis, x, m, &Max);
        PreProc(Dis, Sht, x, m);

        /*Searching Phase--------------*/
        count = 0;
        j = m - 1;
        jMax = Max - m + 1;
        xMax = x[Max];
        memcpy(y + n, x, m);
        while (j < n) {
            while (y[j + jMax] != xMax) j = j + Hors[y[j]];

            q = m - 1;
            Pos = 1 - m + j;
            while ((q >= 0) && (x[q] == y[q + Pos]))
                q--;

            if ((q < 0) && (j < n)) {
                count++;
                q++;
            }

            j = j + Sht[q];
        }
        return count;
    }
};

#endif //ESTIMATINGSTRINGPATTERNALGORITHMS_SSM_H