OneEditDistance.java

package string;

/**
 * Created by gouthamvidyapradhan on 09/12/2017.
 *
 * Given two strings S and T, determine if they are both one edit distance apart.
 */
public class OneEditDistance {

    /**
     * Main method
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception{
        System.out.println(new OneEditDistance().isOneEditDistance("abxd", "adxb"));
    }

    public boolean isOneEditDistance(String s, String t) {
        if(Math.abs(s.length() - t.length()) > 1 || s.equals(t)) return false;
        if(s.length() > t.length()){
            return hasDiffOne(s, t, false);
        } else if(t.length() > s.length()){
            return hasDiffOne(t, s, false);
        } else{
            return hasDiffOne(s, t, true);
        }
    }

    private boolean hasDiffOne(String s, String t, boolean sameLength){
        int count = 0, i = 0, j = 0;
        for(int l1 = s.length(), l2 = t.length(); i < l1 && j < l2;){
            if(s.charAt(i) == t.charAt(j)){
                i++; j++;
            } else{
                if(count > 0) return false;
                count++;
                if(sameLength){
                    i++; j++;
                } else{
                    i++;
                }
            }
        }
        if(i == j){
            return true;
        } else{
            return (s.charAt(s.length() - 1) == t.charAt(t.length() - 1));
        }
    }
}