From fa4f9d7acdcb9842650b7530b42af2c910946b78 Mon Sep 17 00:00:00 2001
From: blackviper0820 <56683166+blackviper0820@users.noreply.github.com>
Date: Tue, 29 Oct 2019 23:43:17 +0530
Subject: [PATCH] Chetan.cpp

---
 Rabin-karp/Chetan.cpp | 79 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 Rabin-karp/Chetan.cpp

diff --git a/Rabin-karp/Chetan.cpp b/Rabin-karp/Chetan.cpp
new file mode 100644
index 0000000..e2c3b65
--- /dev/null
+++ b/Rabin-karp/Chetan.cpp
@@ -0,0 +1,79 @@
+/* Following program is a C++ implementation of Rabin Karp 
+Algorithm given in the CLRS book */
+#include <bits/stdc++.h> 
+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<<endl; 
+		} 
+
+		// Calculate hash value for next window of text: Remove 
+		// leading digit, add trailing digit 
+		if ( i < N-M ) 
+		{ 
+			t = (d*(t - txt[i]*h) + txt[i+M])%q; 
+
+			// We might get negative value of t, converting it 
+			// to positive 
+			if (t < 0) 
+			t = (t + q); 
+		} 
+	} 
+} 
+
+/* Driver code */
+int main() 
+{ 
+	char txt[] = "GEEKS FOR GEEKS"; 
+	char pat[] = "GEEK"; 
+	int q = 101; // A prime number 
+	search(pat, txt, q); 
+	return 0; 
+} 
+
+// This is code is contributed by rathbhupendra