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KMP.java
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KMP.java
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/*
KMP algorithm
Time complexity : O(n + m)
Space complexity : O(m)
where n = length of txt
m = length of pattern
*/
import java.util.*;
public class KMP{
static void KMPSearch(String txt, String pat, int lps[]){
int i=0, j=0;
int n = txt.length(), m = pat.length();
while(i<n){
if(txt.charAt(i) == pat.charAt(j)){
i++; j++;
}
if(j==m){
System.out.print((i-j) + " ");
j = lps[j-1];
}else if(i<n && txt.charAt(i)!=pat.charAt(j)){
if(j==0)
i++;
else
j = lps[j-1];
}
}
}
static void fillLPS(String str, int lps[]){
int len = 0, n = str.length();
lps[0] = 0;
int i=1;
while(i<n){
if(str.charAt(i)==str.charAt(len)){
len++;
lps[i] = len;
i++;
}else{
if(len==0){
lps[i]=0;
i++;
}else{
len = lps[len-1];
}
}
}
}
public static void main(String[] args) {
String txt = "Happy coding! && Enjoy coding";
String pat = "od";
int lps[] = new int[pat.length()];
fillLPS(pat, lps);
System.out.print("Starting indices in txt where pattern(pat) found:");
KMPSearch(txt, pat, lps);
}
}