Added KMP for pattern Searching

Author: varun514

KMP/C++/kmp.cpp

@@ -0,0 +1,54 @@
+//Knuth-Patt-Morris Algorithm for pattern searching in given string
+
+
+/*
+    txt is text and pat is the pattern to be searched
+    vector pos stores the end position where pattern is found
+    (0-based indexing)
+    Time Conmplexity: O(pat.length + txt.length)
+        */
+ 
+#include <bits/stdc++.h>
+using namespace std;      
+        
+vector<int> kmp(string txt, string pat) 
+{
+	string s = pat + '$' + txt;
+	int n = s.length(), l = pat.length();
+	vector<int> LPS(n, 0);
+	int k = 0;
+
+	/* Building LPS Array */
+	for(int i = 1; i < n; ++i)
+	{
+		while(k > 0 && s[i] != s[k])
+		{
+			k = LPS[k-1];
+		}
+		if (s[i] == s[k]) 
+		    ++k;
+		LPS[i] = k;
+	}
+	/* Searching for pattern and storing occurences in vector i.e the index where pattern ends */
+	vector<int> pos;
+	for(int i = 0; i < n; ++i)
+	{
+		if (LPS[i] == l)
+		{
+			pos.push_back(i-l-1);
+		}
+	}
+	return pos;
+}
+
+int main()
+{
+	string text,pattern;
+	cin>>text>>pattern;
+	vector<int> ans=kmp(text,pattern);
+	for(auto y:ans)
+	{
+		cout<<y+1<<endl;
+	}
+	return 0;
+}