KMP Agorithm (Part 2 : Complete Algorithm)

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Tue Feb 08 2022 12:05:47 GMT+0000 (UTC)

Saved by @Uttam #java #gfg #geeksforgeeks #lecture #string #patternsearching #kmp #lps

import java.util.*;
import java.io.*;
  
class GFG { 

    static void fillLPS(String str, int lps[])
    {
        int n=str.length(),len=0;
        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];}
            }
        }
    }

    static void KMP(String pat,String txt)
    {
        int N=txt.length();
        int M=pat.length();
        int[] lps=new int[M];
        fillLPS(pat,lps);
        int i=0,j=0;
        while(i<N){
            if(pat.charAt(j)==txt.charAt(i)){i++;j++;}
    
            if (j == M) { 
                System.out.println("Found pattern at index " + (i - j));
                j = lps[j - 1]; 
            } 
            else if (i < N && pat.charAt(j) != txt.charAt(i)) { 
                if (j == 0) 
                    i++;
                else
                    j = lps[j - 1];  
            }
        }
    }

    public static void main(String args[]) 
    {   String txt = "ababcababaad",pat="ababa";
        KMP(pat,txt);
    }  
     
} 
content_copyCOPY

Complete KMP algorithm is discussed. This algorithm uses the LPS array. Input : -------- Text = "ababcababaad" Pattern ="ababa" Output: --------- Found pattern at index 5