Leetcode-One Edit Distance

Given two strings S and T, determine if they are both one edit distance apart.

Analysis:

Must be exactly one distance apart. Not the same.

Solution:

public class Solution {
    public boolean isOneEditDistance(String s, String t) {
        if (s.length()==0 && t.length()==0) return false;
        if (s.length()+t.length()==1) return true;
        
        if (Math.abs(s.length()-t.length())>1) return false;        

        if (s.length()==t.length()) return isOneReplace(s,t);

        if (s.length()>t.length()) return isOneInsert(s,t);
        else return isOneInsert(t,s);
        
    }

    public boolean isOneInsert(String a, String b){
        //a is 1 char longer than b, we determine whether a and b is one insertion distance.

        boolean modified = false;

        int index1 = 0;
        int index2 = 0;

        while (index2<b.length()){
            if (a.charAt(index1)==b.charAt(index2)){
                index1++;
                index2++;
            } else {
                if (modified) return false;
                else {
                    index1++;
                    modified = true;
                }
            }
        }
        return true;
    }


    public boolean isOneReplace(String a, String b){
        //a and b have the same length, we determine whether they are one replace aparted.
        boolean modified = false;
        int index1=0;
        while (index1<a.length())
            if (a.charAt(index1)==b.charAt(index1))
                index1++;
            else if (modified) return false;
            else {
                index1++;
                modified = true;
            }
        if (modified) return true;
        else return false;
    }
              
 
        
    
}