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Grokking the Coding Interview Patterns in C++

Word Ladder

Explore how to use breadth-first search to solve the Word Ladder problem by finding the shortest transformation sequence between two words. Understand the problem constraints and learn to implement an efficient solution that checks single-character differences and sequences from a given word list.

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Statement

Given two words, src and dest, and a list, words, return the number of words in the shortest transformation sequence from src to dest. If no such sequence can be formed, return 00.

A transformation sequence is a sequence of words ((src →\to word1word_1 →\to word2word_2 →\to word3word_3 ...... →\to wordjword_j )) that has the following properties:

  • wordj=word_j = dest
  • Every pair of consecutive words differs by a single character.
  • All the words in the sequence are present in the words. The src does not need to be present in words.

Constraints:

  • 1≤1 \leq src.length ≤10\leq 10

  • src.length == dest.length == words[i].length

  • src ≠\neq dest

  • 1≤1 \leq words.length ≤5000\leq 5000

  • No duplicates in the words

  • src, dest, and words[i] consist of lowercase English characters.

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Word Ladder

1.

What’s the correct output for the following inputs?

src = “hit”

dest = “cog”

words = [“log”, “dot”, “lot”, “dog”, “hot”, “cog”]

A.

5

B.

6

C.

0

D.

7

1 / 3

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground.

C++
usercode > main.cpp
#include <iostream>

#include <vector>



int WordLadder(std::string src, std::string dest, const std::vector<std::string>& words) {

    

    // Replace this placeholder return statement with your code

    return -1;

}
Word Ladder