1.5 One Away: There are three types of edits that can be performed on strings: insert a character, remove a character, or replace a character. Given two strings, write a function to check if they are one edit (or zero edits) away.
EXAMPLE
pale, pIe -> true
pales. pale -> true
pale. bale -> true
pale. bake -> false

public class Solution {
    public static boolean canReplaceOneChar(String s, String t) {
        int count = 0, len_s = s.length(), len_t = t.length();
        for (int i = 0, j = 0; i < len_s && j < len_t; i++, j++) {
            if (s.charAt(i) != t.charAt(j))    
                count++;
        }
        if (count != 1)
            return false;
        else
            return true;   
    }

    public static boolean canDeleteOneChar(String s, String t) {
        int len_s = s.length(), len_t = t.length();
        for (int i = 0, j = 0; i < len_s && j < len_t; i++, j++) {
            if (s.charAt(i) != t.charAt(j)) {
                return s.substring(i + 1).equals(t.substring(j));
            }
        }
        return true;
    }

    public static boolean isOneEditDistance(String s, String t) {
        if (s.equals(t))
            return false;
        int len_s = s.length(), len_t = t.length();
        if (Math.abs(len_s - len_t) > 1)
            return false;
        if (len_s - len_t == 1) {
            return canDeleteOneChar(s, t);
        }
        if (len_t - len_s == 1) {
            return canDeleteOneChar(t, s);
        }
        if (len_s == len_t) {
            return canReplaceOneChar(s, t);
        }
    
        return true;
    }
}