Rabin_Karp Code in Cpp (thuva4#889)

* Rabin_Karp Code in Cpp Commit

* Rename algorithms/C++/RabinKarp_String_Matching/RabinKarp.cpp to algorithms/C++/RabinKarp/RabinKarp.cpp

Co-authored-by: Thuvarakan Tharmarajasingam <17289840+Thuva4@users.noreply.github.com>

Author: Jatin7385

CONTRIBUTING.md

@@ -181,3 +181,4 @@ Unfortunately, sometimes the bug can be only reproduced in your project or in yo
 - [ir2010](https://github.com/ir2010)
 - [Cc618](https://github.com/Cc618)
 - [Md Azharuddin](https://github.com/azhar1038)
+- [Jatin7385](https://github.com/Jatin7385)

algorithms/C++/RabinKarp/RabinKarp.cpp

@@ -0,0 +1,70 @@
+//Rabin Karp Implementation in CPP
+// Code by Jatin Dhall
+#include <iostream>
+#include <cmath>
+using namespace std;
+
+//Subtracting each character by 96 so that lowercase alphabets start from 1
+int calculateHash(string pattern)//Function to calculate the hash value of the pattern
+{
+    int n = pattern.length();
+    int hash = 0;
+    for(int i=0;i<n;i++)
+    {
+        hash += ((pattern[i] - 96) * pow(10,(n-i-1))); // Formula to calculate the hash value while avoiding Spurious Hits
+    }
+    return hash;
+}
+
+int check(string substring, string pattern)//Function to check whether the characters are same bw the pattern and the substring
+//(Substring is the string of length m, that had the same hash value as the pattern)
+{
+    for(int i=0;i<pattern.length();i++)
+    {
+        if(pattern.at(i) != substring.at(i))
+        {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+void search(string text,string pattern)//Function that conducts the pattern matching 
+{
+    int hash = calculateHash(pattern);
+    int hash1;
+    string substring;
+    int n = text.length(),m = pattern.length();
+    for(int i=0;i<n;i++)
+    {
+        hash1 = 0;
+        substring = "";
+
+        if(n - i < m){break;}//Checking if the remaining no. of characters is less thn the length of the pattern
+        
+        for(int j = 0; j<m;j++)//Calculating the hash value of the substring of length m from text
+        {
+            substring += text[i+j];
+            hash1 += ((text[i + j] - 96) * pow(10,(m-j-1)));
+        }
+        if(hash == hash1) //If the hash value of the substring is the same as that of the pattern, then check each characters
+        {
+            int res = check(substring,pattern); // Check
+            if(res == 1)
+            {
+                cout<<"Pattern found at : "<<i+1<<"'th Position"<<endl;
+            }
+        }
+    }
+}
+
+int main()
+{
+    string text,pattern;
+    cout<<"Enter the text : ";
+    cin>>text;
+    cout<<"Enter the pattern : ";
+    cin>>pattern;
+    search(text,pattern);
+    
+}