Problem Statement A word ladder is a sequence of words in which each word can be transformed into the next word by changing one letter. For example, the word ladder below changes 'lot' to 'log'.
lot dot dog log
This is not the shortest word-ladder between 'lot' and 'log' since the former can be immediately changed to the latter yielding a word ladder of length two:
lot log
The first and last words in a word ladder are the anchor rungs of the ladder. Any other words are interior rungs. For example, there are three interior rungs in the ladder below between 'smile' and 'evote'.
smile smite smote emote evote
In this problem you'll write a method that has parameters representing potential interior rungs: a vector of strings (these may by nonsense or English words), and the anchor rungs --- two strings. Your code must determine the shortest word ladder between the anchor rungs that uses at least one interior rung. Return the length of the shortest valid word ladder. If there are no valid ladders return 0.
Notes and Constraints
The parameters from and to are the anchor rungs, they must be connected by at least one interior rung from words or there are no valid word ladders.
words contains at most 50 words.
All strings contain only lowercase, alphabetic characters.
All strings in word are the same length and are the same length as fromand to.
Examples
words = [hot, dot, dog]
from = hit
to = cog
Returns: 5
The only ladder is hit hot dot dog cog which has length five.
words = [hot, dot, dog, lot, log]
from = hit
to = cog
Returns: 5
Now there are two length-five ladders:
hit hot dot dog cog
hit hot lot log cog
words = [rain, ruin, gain, grin, grit, main, pain, pair, pail, mail]
from = sail
to = ruip
Returns: 6
There are two ladders of length six and no shorter ladders.
sail mail main rain ruin ruip
sail pail pain rain ruin ruip
words = [most, mist, fist, fish]
from = lost
to = cost
Returns: 3
Although lost is directly connected to cost, a valid word ladder must contain an interior rung so the shortest ladder is
lost most cost
words = [mist, fist, fish]
from = lost
to = cost
Returns: 0
Although lost is directly connected to cost, a valid word ladder must contain an interior rung, and there is no such ladder.
Given Function
#include
#include
int shortest(vector words, string from, string to) {
// fill in code here
}