Wagner Fischer algorithm implementation in java

I am trying to implement the Wagner-Fischer algorithm in java using the Wikipedia reference

wagner-fischer

Java Code:

public class StringDistance {

public static void main(String[] args) {
    int i, j, m, n, temp, tracker;

    int[][] d = new int[50][50];

    String s = "kitten";
    String t = "sitting";

    char u[] = s.toCharArray();
    char v[] = t.toCharArray();

    m = u.length;
    n = v.length;

    for (i = 0; i <= m; i++) {
        d[i][0] = i;
    }
    for (j = 0; j <= n; j++) {
        d[0][j] = j;
    }

    for (j = 1; j <= m; j++) {
        for (i = 1; i <= n; i++) {
            if (u[i - 1] == v[j - 1]) {
                tracker = 0;
            } else {
                tracker = 1;
            }

            temp = Math.min((d[i - 1][j] + 1), (d[i][j - 1] + 1));
            d[i][j] = Math.min(temp, (d[i - 1][j - 1] + tracker));

        }
    }

    System.out.println("The levenstien distance" + d[n][m]);
}
}

But the above code is working only for the strings with equal lengths. If i want to make this work for unequal strings.Please let me know how to overcome the issue.

I am getting the index out of bounds error : 

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
at StringDistance.main(StringDistance.java:32)
Jon Skeet
people
quotationmark

Let's get rid of some of the local variables to make it clearer why this is happening:

for (j = 1; j <= u.length; j++) {
    for (i = 1; i <= v.length; i++) {
        if (u[i - 1] == v[j - 1]) {
            tracker = 0;
        } else {
            tracker = 1;
        }

You're using i - 1 (which is guaranteed to be in range for v) as the index into u and j - 1 (which is guaranteed to be in range for u) as the index into v.

So I suspect this expression:

u[i - 1] == v[j - 1]

should just be

u[j - 1] == v[i - 1]

I'd also strongly suggest only declaring variables at the point of first use, in minimal scope, and using 0-based indexing rather than 1-based. And the conditional operator helps too. So your loop would become:

for (int j = 0; j < u.length; j++) {
    for (int i = 0; i < v.length; i++) {
        int tracker = u[j] == v[i] ? 0 : 1;
        int temp = Math.min(d[i][j + 1] + 1, d[i + 1][j] + 1);
        d[i + 1][j + 1] = Math.min(temp, d[i][j] + tracker);
    }
}

people

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