Added Rabin-Karp Algorithm

Author: archie94

algorithm/category.json

@@ -50,7 +50,8 @@
    		"name": "String",
    		"list": {
    			"edit_distance": "Edit Distance",
-   			"knuth_morris_pratt": "KMP Substring Search"
+   			"knuth_morris_pratt": "KMP Substring Search",
+        "rabin_karp_algorithm": "Rabin-Karp Algorithm"
    		}
    },
    "dp": {

algorithm/string/rabin_karp_algorithm/basic/code.js

@@ -0,0 +1,57 @@
+var N = text.length;
+var M = pattern.length;
+
+var hashText = 0; //hash value for text
+var hashPattern = 0; //hash value for pattern
+var h = 1;
+
+for ( var i = 0; i <  (M - 1); i++ ) {
+	h = ( h * D ) % Q;
+}
+
+for ( var i = 0; i < M; i++ ) {
+	hashPattern = ( D * hashPattern + pattern[i].charCodeAt(0)) % Q;
+	hashText = ( D * hashText + text[i].charCodeAt(0)) % Q;
+}
+
+for ( var i = 0 ; i <= N-M; i++ ) {
+
+	/*
+	Check if hash values of current window of text matches 
+	with hash values of pattern. If match is found then 
+	check for characters one by one
+	*/
+	if ( hashPattern === hashText ) {
+		var f = 0;
+		tracer1._select( i, i + M )._wait();
+		tracer2._select( 0, M - 1 )._wait();
+		for( var j = 0; j < M; j++ ) {
+
+			tracer1._notify( i + j )._wait();
+			tracer2._notify( j )._wait();
+			if ( text[i + j] != pattern[j] ) {
+				f++;
+			}
+			tracer1._denotify( i + j );
+			tracer2._denotify( j );
+		}
+
+		if( f === 0 ) {
+			logger._print( ' Pattern found at index ' + i );
+		}
+		tracer1._deselect( i, i + M );
+		tracer2._deselect( 0, M - 1 );
+	}
+
+	/*
+	Calculate hash value for next window of text :
+	*/
+	if ( i < N-M ) {
+		hashText = ( D * ( hashText - text[i].charCodeAt(0)*h ) + text[ i + M ].charCodeAt(0) ) % Q;
+
+		// Convert negative value of hashText (if found) to positive
+		if ( hashText < 0 ) {
+			hashText = hashText + Q;
+		}
+	}
+}

algorithm/string/rabin_karp_algorithm/basic/data.js

@@ -0,0 +1,9 @@
+var text = ['h','e','l','l','o',' ','s','i','r',' ','h','e','l','l','o'];
+var pattern = ['h','e','l','l','o'];
+
+var Q = 101; // A prime number 
+var D = 256; // number of characters in the input alphabet
+
+var logger = new LogTracer();
+var tracer1 = new Array1DTracer('Text')._setData(text);
+var tracer2 = new Array1DTracer('Pattern')._setData(pattern);

algorithm/string/rabin_karp_algorithm/desc.json

@@ -0,0 +1,16 @@
+{
+  "Rabin–Karp Algorithm": "Rabin–Karp algorithm or Karp–Rabin algorithm is a string searching algorithm created by Richard M. Karp and Michael O. Rabin (1987) that uses hashing to find any one of a set of pattern strings in a text.",
+  "Applications": [
+    "Substring Search"
+  ],
+  "Complexity": {
+    "time": " O(N) : If a sufficiently large prime number is used for the hash function. O(MN) : Worst Case ",
+    "space": "O( 1 )"
+  },
+  "References": [
+    "<a href='https://en.wikipedia.org/wiki/Rabin%E2%80%93Karp_algorithm'>Wikipedia</a>"
+  ],
+  "files": {
+    "basic": "Rabin-Karp Algorithm"
+  }
+}