Question

Hello fellow programmers,

I would like to ask for some help with regards to near matches of strings.

Currently, I have a program that stores strings of description, users can search for description by typing it completely or partially.

I would like to implement a near match search. For example the actual description is “hello world” but user erroneously enter a search “hello eorld”. The programs should be able to return “hello world” to user.

I’ve tried looking at pattern and matches to implement it, but it requires a regex to match strings, whereby my description does not have a regular pattern. I’ve also tried string.contains, but it doesn’t seems to work either. Below is part of the code i tried to implement.

    ArrayList <String> list = new ArrayList<String>();
    list.add("hello world");
    list.add("go jogging at london");
    list.add("go fly kite");
    Scanner scan = new Scanner(System.in);

    for(int i = 0; i < list.size(); i++){
      if(list.get(i).contains(scan.next())) {
         System.out.println(list.get(i));
      }
    }

Could fellow programmers help me with this??

Answer 1

You can use LCS(Longest Common Subsequence) see these:
http://en.wikipedia.org/wiki/Longest_common_subsequence_problem

public class LCS {

    public static void main(String[] args) {
        String x = StdIn.readString();
        String y = StdIn.readString();
        int M = x.length();
        int N = y.length();

        // opt[i][j] = length of LCS of x[i..M] and y[j..N]
        int[][] opt = new int[M+1][N+1];

        // compute length of LCS and all subproblems via dynamic programming
        for (int i = M-1; i >= 0; i--) {
            for (int j = N-1; j >= 0; j--) {
                if (x.charAt(i) == y.charAt(j))
                    opt[i][j] = opt[i+1][j+1] + 1;
                else 
                    opt[i][j] = Math.max(opt[i+1][j], opt[i][j+1]);
            }
        }

        // recover LCS itself and print it to standard output
        int i = 0, j = 0;
        while(i < M && j < N) {
            if (x.charAt(i) == y.charAt(j)) {
                System.out.print(x.charAt(i));
                i++;
                j++;
            }
            else if (opt[i+1][j] >= opt[i][j+1]) i++;
            else                                 j++;
        }
        System.out.println();

    }

}

Other solution is Aho–Corasick string matching algorithm see this :
Fast algorithm for searching for substrings in a string