C++ Program to Implement Rabin-Karp Algorithm

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This C++ Program demonstrates the implementation of Rabin-Karp Algorithm.

Here is source code of the C++ Program to demonstrate the implementation of Rabin-Karp Algorithm. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

  1. /*
  2.  * C++ Program to Implement Rabin-Karp Algorithm
  3.  */
  4. #include <iostream>
  5. #include <cstdio>
  6. #include <cstring>
  7. #include <cstdlib>
  8. using namespace std;
  9. #define d 256
  10. /*
  11.  * search a substring in a string 
  12.  */
  13. void search(char *pat, char *txt, int q)
  14. {
  15.     int M = strlen(pat);
  16.     int N = strlen(txt);
  17.     int i, j;
  18.     int p = 0;
  19.     int t = 0;
  20.     int h = 1;
  21.     for (i = 0; i < M - 1; i++)
  22.         h = (h * d) % q;
  23.     for (i = 0; i < M; i++)
  24.     {
  25.         p = (d *p + pat[i]) % q;
  26.         t = (d * t + txt[i]) % q;
  27.     }
  28.     for (i = 0; i <= N - M; i++)
  29.     {
  30.         if (p == t)
  31.         {
  32.             for (j = 0; j < M; j++)
  33.             {
  34.                 if (txt[i + j] != pat[j])
  35.                     break;
  36.             }
  37.             if (j == M)
  38.             {
  39.                 cout<<"Pattern found at index: "<<i<<endl;
  40.             }
  41.         }
  42.         if (i < N - M)
  43.         {
  44.             t = (d * (t - txt[i] * h) + txt[i + M]) % q;
  45.             if (t < 0)
  46.               t = (t + q);
  47.         }
  48.     }
  49. }
  50.  
  51. /* Main */
  52. int main()
  53. {
  54.     char *txt = "Sanfoundry Linux Training";
  55.     char *pat = "nux";
  56.     int q = 101;
  57.     search(pat, txt, q);
  58.     return 0;
  59. }

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$ g++ rabinkarp.cpp
$ a.out
 
Pattern found at index: 13
 
------------------
(program exited with code: 1)
Press return to continue

Sanfoundry Global Education & Learning Series – 1000 C++ Programs.

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If you wish to look at all C++ Programming examples, go to C++ Programs.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn