MakerSquare Trie Autocomplete Hints

Hints for the Trie Autocomplete project.

Transcript

1. Stuck? Keep on reading!
2. includes(string) Returns true if string is in the trie. Strategy: recursively walk each character and node.
 
 Base case: string is length 1. Recursive case: node has children that matches next character.
3. b i s d o g t _includes(“dog”, head) includes(“dog”) => true
4. b i s d o g t _includes(“dog”, head) _includes(“og”, head.children[“d”])
5. b i s d o g t _includes(“dog”, head) _includes(“og”, head.children[“d”]) _includes(“g”, node.children[“o”])
6. b i s d o g t _includes(“dog”, head) _includes(“og”, head.children[“d”]) Base case (length is one):
 return true if g is stop node. _includes(“g”, node.children[“o”])
7. b i s d o g t _includes(“dog”, head) _includes(“og”, head.children[“d”]) true _includes(“g”, node.children[“o”])
8. b i s d o g t _includes(“dog”, head) true true
9. b i s d o g t true true true
10. _includes(“dog”, head) _includes(“og”, head.children[“d”]) _includes(“g”, node.children[“o”]) return true
11. true true true return true includes(“dog”) => true
12. this.includes  =  function(string)  {
    if  (!string  ||  string.length  ===  0)
        return  false;
 
    return  this._includes(string,  this.head);
 }
 
 this.includes  =  function(string,  node)  {
    //  TODO  WRITE  CODE  HERE
 }
13. Questions?
14. iterate(node) Returns all substrings under this node. trie.iterate(bNode) => [“bats”, “bat”, “bad”, “bid”] b a i t s d d d o g t
15. iterate(node) Returns all substrings under this node. Strategy: recursively walk each character and node.
 
 Base case: no nodes left to iterate. Recursive case: iterate through each child, inserting substrings into a list.
16. trie.iterate(undefined/null) => []
 trie.iterate(head) => []
17. trie.iterate(undefined/null) => []
 trie.iterate(head) => [] ! trie.iterate(node) => [“b”] b
18. trie.iterate(node) b a i t d bat
 bad
 bi
19. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0])
20. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(aNode.children[0])
 => [“t”]
21. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(aNode.children[0])
 => [“t”] strings = [“at”]
22. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”]
23. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”, “ad”]
24. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”, “ad”] strings =[“bat”, “bad”]
25. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(node.children[1])
 => [“i”] trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”, “ad”] strings =[“bat”, “bad”]
26. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(node.children[1])
 => [“i”] trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”, “ad”] strings =[“bat”, “bad”, “bi”]
27. Questions?
28. b i s d o g t _includes(“dog”, head) _includes(“og”, head.children[“d”]) Base case (length is one):
 return true if g is stop node. _includes(“g”, node.children[“o”])
29. trie.iterate(node) b a i t d bat
 bad
 bi trie.iterate(node.children[0]) trie.iterate(node.children[1])
 => [“i”] trie.iterate(aNode.children[0])
 => [“t”] trie.iterate(aNode.children[1])
 => [“d”] strings = [“at”, “ad”] strings =[“bat”, “bad”, “bi”]
30. Code Hints
31. Hint 1: includes() base case this._includes  =  function(substring,  node)  {
    if  (substring.length  ===  1  &&
            node  &&  node.children[substring])  {
        //  If  this  node  is  a  stop  node,
        //  then  the  string  exists.
        //  Otherwise,  the  string  doesn't  exist.
        
        //  TODO  WRITE  CODE  HERE
    }
 
    //  Recursive  case  goes  here.
 }  
32. Hint 2: includes() recursive case this._includes  =  function(substring,  node)  {
    //  Base  case  goes  here.
 
    var  child  =  node.children[substring[0]];
    if  (child)  {
        //  This  character  exists  in  the  tree.  Go  one  layer  down.
 
        //  TODO  WRITE  CODE  HERE
    }  else  {
        //  There  is  no  next  node  to  go  to.
        //  String  does  not  exist.
 
        //  TODO  WRITE  CODE  HERE
    }
 }  
33. Hint 3: iterate() base cases this.iterate  =  function(node)  {
    if  (!node)  {
        return  [];
    }   
    if  (this.isEmpty(node.children))  {
        //  This  is  a  leaf  node.  Return  the  value.
        //  Handle  case  if  node  is  head.
        if  (node.value)  {
            return  [node.value];
        }  else  {
            return  [];
        }
    }
 
    //  TODO  WRITE  CODE  HERE
 }
34. this.iterate  =  function(node)  {
    //  BASE  CASES  HERE
 
    var  strings  =  [];
    for  (var  char  in  node.children)  {
        var  child  =  node.children[char];
        var  childStrings  =  this.iterate(child);
        for  (var  i  in  childStrings)  {
            //  TODO  WRITE  CODE  HERE
        }
    }
    if  (node.stop)  {
        strings.push(node.value);
    }
    return  strings;
 }; Hint 4: iterate() recursive case