diff --git a/Rabin-Karp Algorithm b/Rabin-Karp Algorithm new file mode 100644 index 0000000..486fce9 --- /dev/null +++ b/Rabin-Karp Algorithm @@ -0,0 +1,79 @@ +#include +using namespace std; + +// d is the number of characters in the input alphabet +#define d 256 + +/* pat -> pattern + txt -> text + q -> A prime number +*/ +void search(char pat[], char txt[], int q) +{ + int M = strlen(pat); + int N = strlen(txt); + int i, j; + int p = 0; // hash value for pattern + int t = 0; // hash value for txt + int h = 1; + + // The value of h would be "pow(d, M-1)%q" + for (i = 0; i < M - 1; i++) + h = (h * d) % q; + + // Calculate the hash value of pattern and first + // window of text + for (i = 0; i < M; i++) + { + p = (d * p + pat[i]) % q; + t = (d * t + txt[i]) % q; + } + + // Slide the pattern over text one by one + for (i = 0; i <= N - M; i++) + { + + // Check the hash values of current window of text + // and pattern. If the hash values match then only + // check for characters on by one + if ( p == t ) + { + /* Check for characters one by one */ + for (j = 0; j < M; j++) + { + if (txt[i+j] != pat[j]) + break; + } + + // if p == t and pat[0...M-1] = txt[i, i+1, ...i+M-1] + if (j == M) + cout<<"Pattern found at index "<< i<