Last active
October 21, 2020 23:41
-
-
Save jianminchen/645117d2c6015518a4824ef452b9d6dc to your computer and use it in GitHub Desktop.
425 word square - C# code - Trie - I took time to figure out prefix.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
using System; | |
using System.Collections.Generic; | |
using System.Linq; | |
using System.Text; | |
using System.Threading.Tasks; | |
namespace _435_word_square | |
{ | |
class Program | |
{ | |
static void Main(string[] args) | |
{ | |
var list = new List<string>() { "abat", "baba", "atan", "atal" }; | |
var result = WordSquares(list); | |
} | |
public class Trie | |
{ | |
public List<int> Indexes; | |
public Trie[] Children; | |
public Trie() | |
{ | |
Children = new Trie[26]; | |
Indexes = new List<int>(); | |
} | |
/// <summary> | |
/// | |
/// </summary> | |
/// <param name="words"></param> | |
/// <returns></returns> | |
public Trie BuildTrie(List<string> words) | |
{ | |
var root = new Trie(); | |
for (int i = 0; i < words.Count; i++) | |
{ | |
var start = root; | |
var word = words[i]; | |
for(int j = 0; j < word.Count(); j++) | |
{ | |
var next = word[j] - 'a'; | |
if (start.Children[next] == null) | |
{ | |
start.Children[next] = new Trie(); | |
} | |
start = start.Children[next]; | |
start.Indexes.Add(i); | |
} | |
} | |
return root; | |
} | |
} | |
/// <summary> | |
/// | |
/// </summary> | |
/// <param name="words"></param> | |
/// <returns></returns> | |
public static List<List<string>> WordSquares(List<string> words) | |
{ | |
var trie = new Trie(); | |
var root = trie.BuildTrie(words); | |
var length = words[0].Length; | |
var output = new string[length]; | |
var result = new List<List<string>>(); | |
foreach (var word in words) | |
{ | |
output[0] = word; | |
runDFS(words, 1, root, output, result); | |
} | |
return result; | |
} | |
/// <summary> | |
/// | |
/// </summary> | |
/// <param name="words"></param> | |
/// <param name="level"></param> | |
/// <param name="root"></param> | |
/// <param name="output"></param> | |
/// <param name="result"></param> | |
private static void runDFS(List<string> words, int level, Trie root, string[] output, List<List<string>> result) | |
{ | |
if (level >= words[0].Count()) | |
{ | |
result.Add(new List<string>(output)); | |
return; | |
} | |
// baba | |
// a | |
// b | |
// a | |
// The idea is that ith column should be same as ith row for i = 0 to 3 | |
var prefix = ""; | |
for (int i = 0; i < level; i++) | |
{ // level - index | |
prefix += output[i][level].ToString(); // find "a" - level 1 | |
} | |
var start = root; | |
for(int i = 0; i < prefix.Length;i++) | |
{ | |
var next = prefix[i] - 'a'; | |
if (start.Children[next] == null) | |
{ | |
return; | |
} | |
start = start.Children[next]; | |
} | |
foreach (var item in start.Indexes) | |
{ | |
output[level] = words[item]; | |
runDFS( words, level + 1, root, output, result); | |
} | |
} | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment