Implement Rabin-Karp algorithm

Author: yanurag1414

src/main/java/com/thealgorithms/strings/RabinKarpAlgorithm.java

@@ -0,0 +1,58 @@
+package com.thealgorithms.strings;
+
+public class RabinKarpAlgorithm {
+    static final int d = 256;
+    static final int q = 101;
+
+    //M = length of pattern
+    // N = length 0f text
+    static void robinKarpSearch(String pat,String txt,int M,int N){
+        int h = 1;
+        for (int i = 1; i <=M-1 ; i++) {
+            h = (h*d)%q;
+        }
+        // Hash-value for pattern
+        // Hash-value for text
+        int p = 0,t = 0;
+        for (int i = 0; i < M; i++) {
+            p = (p*d+pat.charAt(i))%q;
+            t = (t*d+txt.charAt(i))%q;
+        }
+        //Slide the pattern over text one by one
+        for (int i = 0; i <=(N-M) ; i++) {
+            //check the hash values of current window of
+            //text and pattern. if hash-value match then only
+            // check for characters one by one
+            if(p==t){
+                //checking for character one by one
+                boolean flag = true;
+                for (int j = 0; j < M; j++) {
+                    if(txt.charAt(i+j)!=pat.charAt(j)){
+                        flag = false;
+                        break;
+                    }
+                }if (flag==true){
+                    System.out.println(i+" ");
+                }
+            }
+            //Calculate hash-value for next window of text:
+            // Remove leading digit. Add trailing digit
+            if(i<N-M){
+                t = ((d*(t-txt.charAt(i)*h))+txt.charAt(i+M))%q;
+            }
+
+            //We might get negative value of t,
+            // converting it to positive
+            if(t<0){
+                t = t+q;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        String txt = "ABCCDDAEFG";
+        String pat = "CDD";
+        System.out.println("All index numbers where patter found: ");
+        robinKarpSearch(pat,txt,pat.length(),txt.length());
+    }
+}