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Program to Implement String Matching Using Vectors



Program to Implement String Matching Using Vectors

This C++ program implements string matching using vectors. A text and a pattern is given as input. The pattern is searched for in the text and all instances of the pattern are given as output.

    #include<iostream>

    #include<string.h>

    #include<vector>

    using namespace std;

    void input_string(vector<char>& str)

    {

        char a;

        while (1)

        {

            a = getchar();

            if (a == '\n')

            break;

            str.push_back(a);

        }

        return;

    }

    void print_string(vector<char> strn)

    {

        for (std::vector<char>::iterator it = strn.begin();it != strn.end();++it)

        {

            cout<<*it;

        }

        return;

    }

    int match_string(vector<char>& original, vector<char> match)

    {

        vector<char>::iterator p,q, r;

        int i = 0;

        p = original. begin();

        while (r <= match.end() && p <= original.end())

        {

            r = match.begin();

            while (*p != *r && p < original.end())

            {

                p++;

                i++;

            }

            q = p;

            while (*p == *r && r <= match.end() && p<=original.end())

            {

                p++; i++;

                r++;

            }

            if (r >= match.end())

            {

                original.erase(original.begin(), q + 1);

                return (i - match.size() + 1);

            }

            if (p >= original.end())

            return 0;

            p = ++q;

        }

    }

    int main()

    {

        std::vector<char> original,match;

        int i,result,k=0,sum=0;

        cout<<"Enter String:";

        input_string(original);

        cout<<"Enter Search Pattern:";

        input_string(match);

        if (match.size() > original.size())

        {

            cout<<"Error:Original string too small.";

        }

        do

        {

            result = match_string(original, match);

            sum += result;    //to store previous found position

            if (result > 0)

            {

                k++;

                cout<<"\nMatch found from Position = "<<sum;

            }

         } while (result > 0);   //loop to find all patterns

         if (k == 0)

             cout<<"Error:Match Not Found";

         return 0;

    }