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KMP.java
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68 lines (56 loc) · 1.16 KB
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class KMP{
String string;
String pattern;
int[] lps;
KMP(String string,String pattern){
this.string = string;
this.pattern = pattern;
this.lps = new int[pattern.length()];
}
public int kmp() {
this.createLPS();
int i = 0,j= 0;
while(i<this.string.length() && j<this.pattern.length()) {
if(this.string.charAt(i) == this.pattern.charAt(j)) {
i++;
j++;
}
else if(j==0) {
i++;
}
else {
j = this.lps[j-1];
}
}
if(j==pattern.length()) {
return i-pattern.length();
}
return -1;
}
private void createLPS() {
int i=0,j=1;
this.lps[0] = 0;
while(j<this.pattern.length()) {
if(this.pattern.charAt(i) == this.pattern.charAt(j)) {
this.lps[j] = i+1;
i++;
j++;
}
else if(i ==0) { //this is same as because we wont reach this part if they are not equal, this.pattern.charAt(i) != this.pattern.charAt(j) && i ==0
this.lps[j] = 0;
j++;
}
else {
i = this.lps[i-1];
}
}
}
}
public class Main{
public static void main(String args[]) {
String s = "abcabcabd";
String pattern = "abcabd";
KMP kmp = new KMP(s,pattern);
System.out.println(kmp.kmp());
}
}