Merge pull request matthewsamuel95#590 from shashijangra22/new-branch

added kmp algorithm for string matching

String/KMP/kmp.cpp

@@ -0,0 +1,48 @@
+#include<bits/stdc++.h>
+using namespace std;
+int kmp(string text, string pattern){
+	if(pattern.size()==0) return -1;
+	int patLen=pattern.size();
+	int textLen=text.size();
+	int LPS[patLen]={0};
+	int i=1,j=0;
+
+	while(i<patLen){
+		if(pattern[i]==pattern[j]){
+			LPS[i++]=++j;
+		}
+		else{
+			if(j) j=LPS[j-1];
+			else LPS[i++]=0;
+		}
+	}
+	i=j=0;
+	while(i<textLen){
+		if(pattern[j]==text[i]){
+			i++;j++;
+		}
+		if(j==patLen)	return i-j;
+		else{
+			if(i<textLen && pattern[j]!=text[i]){
+				if(j) j=LPS[j-1];
+				else i++;
+			}
+		}
+	}
+	return -1;
+}
+
+int main(){
+	string text,pattern;
+	cout<<"\nEnter text : ";
+	getline(cin>>ws,text);
+	cout<<"\nEnter pattern to search in "<<text<<" : ";
+	getline(cin>>ws,pattern);
+	int index=kmp(text,pattern);
+	if(index>0){
+		cout<<"\nPattern found at : "<<index<<"\n";
+	}
+	else{
+		cout<<"\nPattern not found!\n";
+	}
+}