Word Ladder
Source
Given two words (start and end), and a dictionary,
find the length of shortest transformation sequence from start to end, such that:
Only one letter can be changed at a time
Each intermediate word must exist in the dictionary
Example
Given:
start = "hit"
end = "cog"
dict = ["hot","dot","dog","lot","log"]
As one shortest transformation is "hit" -> "hot" -> "dot" -> "dog" -> "cog",
return its length 5.
Note
Return 0 if there is no such transformation sequence.
All words have the same length.
All words contain only lowercase alphabetic characters.
Java
public class Solution {
public int ladderLength(String start, String end, Set<String> dict) {
LinkedList<String> cur = new LinkedList<String>();
cur.add(start);
dict.add(end);
int step = 0;
while (!cur.isEmpty()) {
LinkedList<String> parents = cur;
cur = new LinkedList<String>();
step++;
for(String q: parents){
if(q.equals(end))
return step;
char[] t = q.toCharArray();
for(int i = 0; i < start.length(); i++){
for(char c = 'a'; c <= 'z'; c++){
char temp = t[i];
t[i] = c;
String s = String.copyValueOf(t);
t[i] = temp;
if(dict.contains(s)){
cur.add(s);
dict.remove(s);
}
}
}
}
}
return 0;
}
}
Reference
Word Ladder