C++ Program to Perform 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.

This C++ program is successfully compiled and tested on our system. The program output is given below.

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/*
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 * C++ Program to Implement String Matching Using Vectors

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 */
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#include<iostream>
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#include<string.h>
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#include<vector>
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using namespace std;
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void input_string(vector<char>& str)
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{
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    char a;
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    while (1)
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    {
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        a = getchar();
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        if (a == '\n')
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        break;
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        str.push_back(a);
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    }
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    return;
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}
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void print_string(vector<char> strn)
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{
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    for (std::vector<char>::iterator it = strn.begin();it != strn.end();++it)

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    {
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        cout<<*it;
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    }
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    return;
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}
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```

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

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{
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    vector<char>::iterator p,q, r;
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    int i = 0;
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    p = original. begin();
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    while (r <= match.end() && p <= original.end())

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    {
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        r = match.begin();
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        while (*p != *r && p < original.end())

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        {
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            p++;
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            i++;
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        }
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        q = p;
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        while (*p == *r && r <= match.end() && p<=original.end())

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        {
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            p++; i++;
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            r++;
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        }
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        if (r >= match.end())
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        {
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            original.erase(original.begin(), q + 1);

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

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        }
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        if (p >= original.end())
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        return 0;
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        p = ++q;
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    }
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}
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```
 
```
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int main()
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{
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    std::vector<char> original,match;
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    int i,result,k=0,sum=0;
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    cout<<"Enter String:";
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    input_string(original);
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    cout<<"Enter Search Pattern:";
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    input_string(match);
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    if (match.size() > original.size())
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    {
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        cout<<"Error:Original string too small.";

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    }
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    do
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    {
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        result = match_string(original, match);

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

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        if (result > 0)
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        {
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            k++;
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            cout<<"\nMatch found from Position = "<<sum;

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

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     if (k == 0)
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         cout<<"Error:Match Not Found";
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     return 0;
```
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}
```

Output:
 
Enter String:all men went to apall mall
Enter Search Pattern:all
 
Match found from Position = 1
Match found from Position = 19
Match found from Position = 24

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