Create Rabin_karp_algo.cpp

C++/Rabin_karp_algo.cpp

@@ -0,0 +1,55 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define d 256
+const int q = 101;
+void RBSearch(string pat, string txt, int M, int N)
+{
+
+    // Compute (d^(M-1))%q
+    int h = 1;
+    for (int i = 1; i <= M - 1; i++)
+        h = (h * d) % q;
+
+    // Compute p and to
+    int p = 0, t = 0;
+    for (int i = 0; i < M; i++)
+    {
+        p = (p * d + pat[i]) % q;
+        t = (t * d + txt[i]) % q;
+    }
+
+    for (int i = 0; i <= (N - M); i++)
+    {
+        // Check for hit
+        if (p == t)
+        {
+            bool flag = true;
+            for (int j = 0; j < M; j++)
+                if (txt[i + j] != pat[j])
+                {
+                    flag = false;
+                    break;
+                }
+            if (flag == true)
+                cout << i << " ";
+        }
+        // Compute ti+1 using ti
+        if (i < N - M)
+        {
+            t = ((d * (t - txt[i] * h)) + txt[i + M]) % q;
+            if (t < 0)
+                t = t + q;
+        }
+    }
+}
+
+int main()
+{
+    string txt = "ABCDDEFGABCDMNOP";
+    string pat = "ABCD";
+    cout << "All index numbers where pattern found:"
+         << " ";
+    RBSearch(pat, txt, 4, 16);
+
+    return 0;
+}