Added KMP Algorithm

Author: Shaily20

src/KMP.cpp

@@ -0,0 +1,49 @@
+#include <iostream>
+#include<bits/stdc++.h>
+using namespace std;
+
+/*
+ * get prefix list
+ */
+vector<int> computePrefix(string str) {
+
+	int m=int(str.length());
+	vector<int> prefix(m);
+	for(int i=1,k=0;i<m;++i)
+	{
+		if(k>0&&str[i]!=str[k])
+			k=prefix[k-1];
+		if(str[k]==str[i])
+			prefix[i]=++k;
+		else
+			prefix[i]=k;
+	}
+
+	return prefix;
+}
+
+void KMP(string &str, string pat) {
+	int m = int(str.length());
+	int n = int(pat.length());
+	vector<int> longestPrefix = computePrefix(pat);
+
+	for (int i = 0, k = 0; i < m; ++i) {
+		if (k > 0 && pat[k] != str[i])
+			k = longestPrefix[k - 1];
+		if (str[i] == pat[k])
+			++k;
+		if (k == n) {
+			cout << i - n + 1 << "\n";
+			//more than one pattern
+			k = longestPrefix[k - 1];
+		}
+
+	}
+}
+
+int main() {
+	string s,p;
+	cin>>s>>p;
+	KMP(s,p);
+	return 0;
+}