Week 8 [item 5 - pattern matching for count]

*All rights reservrd.

*Author: Li Xinhao

*Completion time: December 14, 2017

*Version number: v1.0

*Problem Description: using sequential structure to store strings, write an algorithm to calculate the number of times a specified substring appears in a string. If the substring does not appear, it is 0.

1, Based on the sequential string method library:

Head file:

#ifndef SqString_H_INCLUDED
#define SqString_H_INCLUDED

#define MaxSize 100 / / maximum number of characters
typedef struct
{   char data[MaxSize];         //Define the space that can hold MaxSize characters
    int length;                 //Mark the current actual string length
} SqString;

void StrAssign(SqString &s,char cstr[]);    //String constant cstr assigned to string s
void StrCopy(SqString &s,SqString t);   //Copy string t to string s
bool StrEqual(SqString s,SqString t); //String equality
int StrLength(SqString s);  //String length
SqString Concat(SqString s,SqString t);  //String connection
SqString SubStr(SqString s,int i,int j); //substring
SqString InsStr(SqString s1,int i,SqString s2); //String insertion
SqString DelStr(SqString s,int i,int j) ;   //String deletion
SqString RepStr(SqString s,int i,int j,SqString t);     //String replacement
void DispStr(SqString s);   //Output string




#endif // SqString_H_INCLUDED

Source files:

#include <stdio.h>
#include <malloc.h>
#include "sqString.h";

void StrAssign(SqString &s,char cstr[]) //s is a reference parameter
{   int i;
    for (i=0;cstr[i]!='\0';i++)
        s.data[i]=cstr[i];
    s.length=i;
}
void StrCopy(SqString &s,SqString t)    //s is a reference parameter
{   int i;
    for (i=0;i<t.length;i++)
        s.data[i]=t.data[i];
    s.length=t.length;
}
bool StrEqual(SqString s,SqString t)
{   bool same=true;
    int i;
    if (s.length!=t.length)             //Return 0 when length is not equal
        same=false;
    else
        for (i=0;i<s.length;i++)
            if (s.data[i]!=t.data[i])   //Return 0 when one corresponding character is different
            {   same=false;
                break;
            }
    return same;
}
int StrLength(SqString s)
{
    return s.length;
}
SqString Concat(SqString s,SqString t)
{   SqString str;
    int i;
    str.length=s.length+t.length;
    for (i=0;i<s.length;i++)    //Copy s.data[0..s.length-1] to str
        str.data[i]=s.data[i];
    for (i=0;i<t.length;i++)    //Copy t.data[0..t.length-1] to str
        str.data[s.length+i]=t.data[i];
    return str;
}
SqString SubStr(SqString s,int i,int j)
{   SqString str;
    int k;
    str.length=0;
    if (i<=0 || i>s.length || j<0 || i+j-1>s.length)
        return str;                 //Empty string returned when parameter is incorrect
    for (k=i-1;k<i+j-1;k++)         //Copy s.data[i..i+j] to str
        str.data[k-i+1]=s.data[k];
    str.length=j;
    return str;
}
SqString InsStr(SqString s1,int i,SqString s2)
{   int j;
    SqString str;
    str.length=0;
    if (i<=0 || i>s1.length+1)  //Empty string returned when parameter is incorrect
        return str;
    for (j=0;j<i-1;j++)             //Copy s1.data[0..i-2] to str
        str.data[j]=s1.data[j];
    for (j=0;j<s2.length;j++)       //Copy s2.data[0..s2.length-1] to str
        str.data[i+j-1]=s2.data[j];
    for (j=i-1;j<s1.length;j++)     //Copy s1.data[i-1..s1.length-1] to str
        str.data[s2.length+j]=s1.data[j];
    str.length=s1.length+s2.length;
    return str;
}
SqString DelStr(SqString s,int i,int j)
{   int k;
    SqString str;
    str.length=0;
    if (i<=0 || i>s.length || i+j>s.length+1) //Empty string returned when parameter is incorrect
        return str;
    for (k=0;k<i-1;k++)             //Copy s.data[0..i-2] to str
        str.data[k]=s.data[k];
    for (k=i+j-1;k<s.length;k++)    //Copy s.data[i+j-1..s.length-1] to str
        str.data[k-j]=s.data[k];
    str.length=s.length-j;
    return str;
}
SqString RepStr(SqString s,int i,int j,SqString t)
{   int k;
    SqString str;
    str.length=0;
    if (i<=0 || i>s.length || i+j-1>s.length) //Empty string returned when parameter is incorrect
        return str;
    for (k=0;k<i-1;k++)             //Copy s.data[0..i-2] to str
        str.data[k]=s.data[k];
    for (k=0;k<t.length;k++)        //Copy t.data[0..t.length-1] to str
        str.data[i+k-1]=t.data[k];
    for (k=i+j-1;k<s.length;k++)    //Copy s.data[i+j-1..s.length-1] to str
        str.data[t.length+k-j]=s.data[k];
    str.length=s.length-j+t.length;
    return str;
}
void DispStr(SqString s)
{   int i;
    if (s.length>0)
    {   for (i=0;i<s.length;i++)
            printf("%c",s.data[i]);
        printf("\n");
    }
}

2, Create the source file main.cpp:

#include <stdio.h>
#include "sqString.h"

int str_count(SqString s,SqString t)
{
    int i=0,j=0,count=0;
    while (i<s.length && j<t.length)
    {
        if (s.data[i]==t.data[j])   //Continue to match next character
        {
            i++;                //Main string and substring match next character in turn
            j++;
        }
        else                    //Main string and substring pointer backtracking to start the next matching again
        {
            i=i-j+1;            //The main string matches from the next position
            j=0;                //Substring match from scratch
        }
        //In BF algorithm, there is no following part
        //Add a judgment here to "capture" the generated match
        if (j>=t.length)        //If j has reached the length of the substring, a match is generated
        {
            count++;            //Match times plus 1
            i=i-j+1;            //The main string continues to match from the next position
            j=0;                //Substring match from scratch
        }
    }
    return(count);
}

int main()
{
    SqString s,t;
    StrAssign(s,"accaccacacabcacbab");
    StrAssign(t,"accac");
    printf("s:");
    DispStr(s);
    printf("t:");
    DispStr(t);
    printf("%d\n",str_count(s,t));
    return 0;
}

3, The screenshot of the test results is as follows: