I am working on an assignment in which we must create a 20-questions type game from a binary search tree. We read the tree in from a text file that is formatted like this:
Does it walk on 4 legs?
Does it fly?
*centipede?
Is it an insect?
*bird?
*butterfly?
Does it purr?
Does it howl?
*mouse?
*dog?
*cat?
Later, I am going to allow the user to add to this list. At the moment, however, I am unable to accurately read the list into a binary search tree. I have set it up so that (I think) it will use recursion and return to the previous "current" node pointer when it ends a loop of the function. Currently, however, the current node pointer remains the same.
The below function is passed a vector of the strings from the text file.
string line;
string guess;
bool start = true;
void buildTree(vector<string> gameData, Node* current, int &counter)
{
//fill node with question or answer
//recursive:
// add to the left until we encounter an asterisk
// add to the right
line = gameData[counter];
//if a question
if (line[0] != '*')
{
if (current->getData().empty())
{
current->setData(line);
cout << current->getData() << endl;
}
if (!start)
{
//if noChild is empty AND current isn't a guess, go to noChild
if ((current->getNo()->getData().empty())
&& (current->isGuess() == false))
{
current = current->getNo();
}
//otherwise, go to yes
else {
current = current->getYes();
}
}
while (counter < gameData.size())
{
if (!start) { counter++; }
start = false;
buildTree(gameData, current, counter);
}
}
//if a guess
else
{
//if data is full, go to no
if (current->getData().empty() == false)
{
current = current->getNo();
}
//otherwise, go to yes
else
{
//current = current->getYes();
for (int i = 1; i < line.size(); i++)
{
guess.push_back(line[i]);
}
current->setData(guess);
guess.clear();
cout << current->getData() << endl;
counter++;
current->setGuess(true);
}
}
}
Related
I am new to c++ and am currently learning sfml.
I have set up a system that adds one 'Snowpile' object to the vector. But when I keep hitting errors like "can't increment vector past iterator past end" or that it's outside the scope.
std::vector<Snowpile*> snowpiles;
I want it to check every snowpile for the removed2 bool, and delete the ones that do have it.
for (auto s_it = snowpiles.begin(); s_it != snowpiles.end(); s_it++) {
int sindex = std::distance(snowpiles.begin(), s_it);
if (snowpiles[sindex]->getSprite_S().getGlobalBounds().intersects(player.getSpriteP().getGlobalBounds()) && snowpiles[sindex]->melting == false) {
snowpiles[sindex]->melting = true;
}
else if (snowpiles[sindex]->getSprite_S().getGlobalBounds().intersects(player.getSpriteP().getGlobalBounds()) && snowpiles[sindex]->melting == true) {
snowpiles[sindex]->melting = true;
}
else if (!snowpiles[sindex]->getSprite_S().getGlobalBounds().intersects(player.getSpriteP().getGlobalBounds()) && snowpiles[sindex]->melting == true) {
snowpiles[sindex]->melting = false;
}
snowpiles[sindex]->meltedrem(sindex, snowpiles, m_win);
if (snowpiles[sindex]->removed2 == true)
{
cout << "Detected removed 2 at " << sindex << endl;
//delete snowpiles[sindex];
snowpiles.erase(snowpiles.begin() + sindex - 1);
}
}
The melting parts determine whether the player is on top of a snowpile. The meltdrem functions checks for bool 'melting' == true and then proceeds to start the timer. After a few seconds (+ animations) it sets the bool removed2 to true.
I know that at the program at least sees the bools changing, so thats not it.
Am I simply using vector wrong, or do I need to change something in my loop?
The loop is located in the while(window.isOpen()) loop in int main.
For starters it is unclear why there is used the expression
snowpiles.erase(snowpiles.begin() + sindex - 1);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
instead of
snowpiles.erase(snowpiles.begin() + sindex);
^^^^^^^^^^^^^^^^^^^^^^^^^^
if in a comment you wrote
//delete snowpiles[sindex];
You need to increase the iterator in the for loop only when a current object was not removed.
Change the loop the following way
for (auto s_it = snowpiles.begin(); s_it != snowpiles.end(); ) {
//...
if (snowpiles[sindex]->removed2 == true)
{
cout << "Detected removed 2 at " << sindex << endl;
//delete snowpiles[sindex];
s_it = snowpiles.erase( s_it );
}
else
{
++s_it;
}
}
First of all, this is part of a university course, so whilst a copy-paste solution would do, I'm looking for a bit more depth. I'll be seeing my supervisor tomorrow anyways though.
Now onto the problem. I am implementing Dijkstra's algorithm for 5 linked nodes, A-E, which have their associated costs and links stored in a vector;
struct Node
{
char nodeLink; //adjacent link
int cost; //cost of a link
}; //to use in Dijkstra algorithm
class HeadNode
{
public:
char Name;
bool Visited;
vector<Node> nodes;
HeadNode(char x) { Name = x; Visited = false; }
};
class Graph
{
char Start = 'A';
char StartNode;
char CurrentNode;
char Destination = 'E';
int TotalCost = 0;
vector<HeadNode> hnode;
vector<char> path;
vector<int> weight;
public:
Graph();
void createHeadNode(char X);
void createAdjMatrix();
char LeastDistance(char node);
void printAdjMatrix();
void Dijkstra(char StartNode);
char GetStartNode();
};
int main()
{
Graph graph;
graph.createHeadNode('A');
graph.createHeadNode('B');
graph.createHeadNode('C');
graph.createHeadNode('D');
graph.createHeadNode('E');
graph.createAdjMatrix();
//graph.printAdjMatrix();
graph.Dijkstra(graph.GetStartNode());
system("pause");
return 0;
}
Graph::Graph()
{
}
void Graph::createHeadNode(char x)
{
hnode.push_back(x);
}
In order to properly implement the algorithm, I have created a precursor function, LeastDistance(), within the class graph. I also have a function to get the start node, but that isn't particularly important here;
char Graph::LeastDistance(char node)
{
int smallest = 9999;
char smallestNode;
for (int i = 0; i < hnode.size(); i++)
{
for (int j = 0; j < hnode[i].nodes.size(); ++j)
{
if ((node == hnode[i].Name) && (hnode[i].nodes[j].cost <= smallest) && (hnode[i].Visited == false))
{
smallest = hnode[i].nodes[j].cost;
smallestNode = hnode[i].nodes[j].nodeLink;
}
else
{
hnode[i].Visited = true;
break;
}
}
}
TotalCost = TotalCost + smallest;
return(smallestNode);
}
void Graph::Dijkstra(char StartNode)
{
CurrentNode = StartNode;
if (CurrentNode == Destination)
{
cout << "the start is the destination, therefore the cost will be 0." << endl;
}
else
{
while(true)
{
if (CurrentNode != Destination)
{
CurrentNode = LeastDistance(StartNode);
cout << CurrentNode << "<-";
}
else if (CurrentNode == Destination)
{
cout << endl;
cout << "The total cost of this path is:" << TotalCost;
TotalCost = 0;//reset cost
break;
}
}
}
}
My problem is that the LeastDistance fucntion appears always to return node C, leading to it being printed over and over, so it fills the console. So far, I have tried to debug using visual studio 2017, but I cant make much sense out of the watches. I have also tweaked the order of the breaks around, and tried to make sure the visited flag is being set to true. whether any precedence of operations is affecting this I am not sure.
Thanks in advance.
I would contend that there are multiple problems with the way you implement this... but I think the one that's causing you the problem you describe is the statement right here:
if (CurrentNode != Destination)
{
CurrentNode = LeastDistance(StartNode);
cout << CurrentNode << "<-";
}
Think about what this does. Let's say your first node isn't the one you're looking for, then you call least distance and find the next smallest node. Then you print it. Then you iterate on the while loop again only to find that CurrentNode isn't the one you're looking for, so you call LeastDistance(StartNode) again, which will return the exactly same value. Thus, you'll keep printing the same result which apparently is c.
Assuming everything else is correct, I think you want:
CurrentNode = LeastDistance(CurrentNode);
I am trying to implement trie data structure in C++ using class. In TrieNode class I have a TrieNode *children[26]; array and an isEndOfWord boolean value to determine if it is the end word. In that same class I have other functions appropriate to function like getters and setters and additionally insert and search.
Whenever I try to add a new word it is also setting the bool value as true at the end of each word by setting true to isEndOfWord. But in searching function it is not determining the end of the word. Please guide me as I am new to this data structure, and please comment on the way i write the code and what is the appropriate way to write it(in a Professional way, if interested). Thanks!
#include<cstdio>
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
using namespace std;
class TrieNode{
private:
TrieNode *children[26];
bool isEndOfWord;
public:
TrieNode(){
for(int i = 0; i < 26; i++){
children[i] = NULL;
}
isEndOfWord = false;
}
bool checkNull(char temp){
cout<<"\nIncheckNULL "<<temp<<" "<<(temp - 'a')<<" \n";
if(children[temp - 'a'] == NULL){
return true;
}
else{
return false;
}
}
void setNode(char temp){
cout<<"Setting node \n";
children[temp - 'a'] = new TrieNode();
}
TrieNode *getNode(char temp){
return children[temp - 'a'];
}
void setEndWord(){
this->isEndOfWord = true;
}
bool getEndWord(){
return this->isEndOfWord;
}
void insert(TrieNode*, string);
bool search(TrieNode*, string);
};
void TrieNode::insert(TrieNode *root, string key){
TrieNode *crawl = root;
//cout<<"key is "<<key<<endl;
int length = sizeof(key)/sizeof(key[0]);
//cout<<"find length\n";
for(int i = 0; key[i] != '\0'; i++){
cout<<"TEST null check key is "<<key[i]<<endl;
if(crawl->checkNull(key[i])){
cout<<"null check key is "<<key[i]<<endl;
crawl->setNode(key[i]);
crawl = crawl->getNode(key[i]);
if(key[i + 1] == '\0'){
cout<<"In setting end word\n";
if(crawl->getEndWord()){
cout<<"Word already exists";
}
else{
crawl->setEndWord();
cout<<"End word setted "<<crawl->getEndWord()<<endl;
}
}
}
else{
if(key[i + 1] == '\0'){
cout<<"In setting end word\n";
if(crawl->getEndWord()){
cout<<"Word already exists";
}
else{
crawl->setEndWord();
cout<<"End word setted\n";
}
}
else{
crawl = crawl->getNode(key[i]);
}
}
}
}
bool TrieNode::search(TrieNode *root, string key){
TrieNode *crawl = root;
cout<<"key is "<<key<<endl;
cout<<"\n In search\n";
int length = sizeof(key)/sizeof(key[0]);
for(int i = 0; key[i] != '\0'; i++){
if(crawl->checkNull(key[i])){
cout<<"INside search checknull"<<endl;
cout<<"Word does not exists"<<"sorry"<<endl;
break;
}
else{
cout<<"IN each character getting getEndWord "<<crawl->getEndWord()<<endl;
if(key[i + 1] == '\0'){
if(crawl->getEndWord()){
cout<<"Word Exists";
}
else{
cout<<"Word does not exists"<<"sorry"<<endl;
break;
}
}
else{
crawl = crawl->getNode(key[i]);
}
}
}
}
int main(){
TrieNode *root = new TrieNode();
cout<<"starting"<<endl;
root->insert(root, "hello");
cout<<"first added"<<endl;
root->insert(root, "anna");
root->insert(root, "anni");
cout<<"words added"<<endl;
root->search(root, "hello");
root->search(root, "anny");
}
Your insert and search functions can be simplified a bit.
Consider this. (Read the comments in the below code, they illustrate what the code does)
void TrieNode::insert(TrieNode *root, string key){
TrieNode *crawl = root;
if (!crawl) {
crawl = new TrieNode();
}
cout << "Adding " << key << " to the trie" << endl;
for (int index = 0, auto str_iterator = str.begin(); str_iterator < str.end(); ++str_iterator, ++index) {
char key_char = *str_iterator;
if(crawl -> checkNull(key_char)){
// If a node representing the char does not exist then make it
crawl -> setNode(key_char);
}
crawl = crawl -> getNode(key_char);
if (index == key.length() - 1) {
// We are at the last character, time to mark an end of word
crawl -> setEndWord();
}
}
}
bool TrieNode::search(TrieNode *root, string key){
TrieNode *crawl = root;
if (!crawl) {
cout << "Trie is empty!" << endl;
return false;
}
cout << "Searching for " << key << " in the trie" << endl;
for (int index = 0, auto str_iterator = str.begin(); str_iterator < str.end(); ++str_iterator, ++index) {
char key_char = *str_iterator;
if(crawl -> checkNull(key_char)){
cout << "Key is not in the trie" << endl;
return false;
}
crawl = crawl -> getNode(key_char);
if (index == key.length() - 1) {
if (!(crawl -> getEndWord())) {
cout << "Word is physically present in trie, but not present as a distinct word" << endl;
return false;
} else {
return true;
}
}
}
cout << "Code should not reach here" << endl; // IMO throw an exception I guess
return false;
}
Take advantage of the power of C++ std::string
Also your whole temp - 'a' logic is a bit iffy to me. I wouldn't much around with ASCII values unless I needed to
Why are you including a whole bunch of C headers? Just iostream should suffice to do what cstdio does.
if(!ptr) is a much more natural way to check for NULL.
In production don't use using namespace std; Instead just preface stuff like cout and endl with std::. The reason for this is to avoid polluting the standard namespace.
Read a good CPP OOP book :). It will help you a lot.
Also I lol'd at anna and anni. Your anna and anni must be proud to be in your trie :D
There are many things I'd give you feedback on, but this isn't a code review site, it's for specific questions. I'll point out briefly a few things I notice though:
1) don't include C headers; use c++ ones instead.
2) what type is string?
3) you compute length (incorrectly, assuming answer to question 2 is "the standard c++ string class"), but you don't use it.
4) search() returns a bool but you don't return anything. When you find the end of a word, you should return from the function.
5) search() calls checkNull() at the top of the for loop without ensuring that it's not null. After this: crawl = crawl->getNode(key[i]); it could be null, but then you loop and go through the pointer without testing it.
6) setNode is a public function, and unconditionally overwrites whatever is in the slot for the given variable. You can clobber an existing child if someone calls it with the same character twice and leak (and probably lose data in your tree.
7) search doesn't need to be a member of TrieNode. In fact, it doesn't access any data through "this". You probably don't want the TrieNode to be public at all, but an internal implenetation detail of Trie, which is where the search function should live, where the root should be stored and managed.
8) in c++ use nullptr instead of NULL
9) Looks like you need to debug search(), because it is not on the last letter when you check for end of word.
10) you need a destructor and need to deallocate your nodes. Or store them in unique_ptr<> for automatic deletion when your object goes out of scope.
11) don't "using namespace std;" in headers. It makes your headers toxic to include in my code.
The insert and search functions are a mess.
They use rather contrived ways to check the end of the string, duplicated unnecessarily and with a bug in one of the branches.
Here are simpler versions.
They use string size for the loop bounds, and the actions needed at the end of the loop are made after the loop, which is more natural.
void TrieNode::insert(TrieNode *root, string key){
TrieNode *crawl = root;
for(int i = 0; i < (int) (key.size()); i++){
if(crawl->checkNull(key[i])){
crawl->setNode(key[i]);
}
crawl = crawl->getNode(key[i]);
}
crawl->setEndWord();
}
bool TrieNode::search(TrieNode *root, string key){
TrieNode *crawl = root;
for(int i = 0; i < (int) (key.size()); i++){
if(crawl->checkNull(key[i])){
return false;
}
crawl = crawl->getNode(key[i]);
}
return crawl->getEndWord();
}
I used the same style, but omitted the debug outputs for readability.
Also, the code did not actually use search as a function, it didn't return a value.
Instead, it relied on debug output to show the result.
This is now corrected.
A main function complementing these is as follows.
int main(){
TrieNode *root = new TrieNode();
cout<<"starting"<<endl;
root->insert(root, "hello");
cout<<"first added"<<endl;
root->insert(root, "anna");
root->insert(root, "anni");
cout<<"words added"<<endl;
cout << root->search(root, "hello") << endl; // 1
cout << root->search(root, "anny") << endl; // 0
}
I'm currently working on a trie implementation for practice and have run into a mental roadbloack.
The issue is with my searching function. I am attempting to have my trie tree be able to retrieve a list of strings from a supplied prefix after they are loaded into the programs memory.
I also understand I could be using a queue/shouldnt use C functions in C++ ect.. This is just a 'rough draft' so to speak.
This is what I have so far:
bool SearchForStrings(vector<string> &output, string data)
{
Node *iter = GetLastNode("an");
Node *hold = iter;
stack<char> str;
while (hold->visited == false)
{
int index = GetNextChild(iter);
if (index > -1)
{
str.push(char('a' + index));
//current.push(iter);
iter = iter->next[index];
}
//We've hit a leaf so we want to unwind the stack and print the string
else if (index < 0 && IsLeaf(iter))
{
iter->visited = true;
string temp("");
stringstream ss;
while (str.size() > 0)
{
temp += str.top();
str.pop();
}
int i = 0;
for (std::string::reverse_iterator it = temp.rbegin(); it != temp.rend(); it++)
ss << *it;
//Store the string we have
output.push_back(data + ss.str());
//Move our iterator back to the root node
iter = hold;
}
//We know this isnt a leaf so we dont want to print out the stack
else
{
iter->visited = true;
iter = hold;
}
}
return (output.size() > 0);
}
int GetNextChild(Node *s)
{
for (int i = 0; i < 26; i++)
{
if (s->next[i] != nullptr && s->next[i]->visited == false)
return i;
}
return -1;
}
bool IsLeaf(Node *s)
{
for (int i = 0; i < 26; i++)
{
if (s->next[i] != nullptr)
return false;
}
return true;
}
struct Node{
int value;
Node *next[26];
bool visited;
};
The code is too long or i'd post it all, GetLastNode() retrieves the node at the end of the data passed in, so if the prefix was 'su' and the string was 'substring' the node would be pointing to the 'u' to use as an artificial root node
(might be completely wrong... just typed it here, no testing)
something like:
First of all, we need a way of indicating that a node represents an entry.
So let's have:
struct Node{
int value;
Node *next[26];
bool entry;
};
I've removed your visited flag because I don't have a use for it.
You should modify your insert/update/delete functions to support this flag. If the flag is true it means there's an actual entry up to that node.
Now we can modify the
bool isLeaf(Node *s) {
return s->entry;
}
Meaning that we consider a leaf when there's an entry... perhaps the name is wrong now, as the leaf might have childs ("y" node with "any" and "anywhere" is a leaf, but it has childs)
Now for the search:
First a public function that can be called.
bool searchForStrings(std::vector<string> &output, const std::string &key) {
// start the recursion
// theTrieRoot is the root node for the whole structure
return searchForString(theTrieRoot,output,key);
}
Then the internal function that will use for recursion.
bool searchForStrings(Node *node, std::vector<string> &output, const std::string &key) {
if(isLeaf(node->next[i])) {
// leaf node - add an empty string.
output.push_back(std::string());
}
if(key.empty()) {
// Key is empty, collect all child nodes.
for (int i = 0; i < 26; i++)
{
if (node->next[i] != nullptr) {
std::vector<std::string> partial;
searchForStrings(node->next[i],partial,key);
// so we got a list of the childs,
// add the key of this node to them.
for(auto s:partial) {
output.push_back(std::string('a'+i)+s)
}
}
} // end for
} // end if key.empty
else {
// key is not empty, try to get the node for the
// first character of the key.
int c=key[0]-'a';
if((c<0 || (c>26)) {
// first character was not a letter.
return false;
}
if(node->next[c]==nullptr) {
// no match (no node where we expect it)
return false;
}
// recurse into the node matching the key
std::vector<std::string> partial;
searchForStrings(node->next[c],partial,key.substr(1));
// add the key of this node to the result
for(auto s:partial) {
output.push_back(std::string(key[0])+s)
}
}
// provide a meaningful return value
if(output.empty()) {
return false;
} else {
return true;
}
}
And the execution for "an" search is.
Call searchForStrings(root,[],"an")
root is not leaf, key is not empty. Matched next node keyed by "a"
Call searchForStrings(node(a),[],"n")
node(a) is not leaf, key is not empty. Matched next node keyed by "n"
Call searchForStrings(node(n),[],"")
node(n) is not leaf, key is empty. Need to recurse on all not null childs:
Call searchForStrings(node(s),[],"")
node(s) is not leaf, key is empty, Need to recurse on all not null childs:
... eventually we will reach Node(r) which is a leaf node, so it will return an [""], going back it will get added ["r"] -> ["er"] -> ["wer"] -> ["swer"]
Call searchForStings(node(y),[],"")
node(y) is leaf (add "" to the output), key is empty,
recurse, we will get ["time"]
we will return ["","time"]
At this point we will add the "y" to get ["y","ytime"]
And here we will add the "n" to get ["nswer","ny","nytime"]
Adding the "a" to get ["answer","any","anytime"]
we're done
I am programming a MARIE assembler for one of my classes and I've ran into a logical error involving my control structure for one of my functions.
What I'm trying to accomplish is taking in all the data that was inserted into my vectors and then that data is being used to create integer opcode data for display. Yet for whatever reason my nested for loop is being ignored after my if-else chain.
The code within the nested for-loop seems to be working properly aside from this one logic error.
Please note that instructions, hexNums, secondPassData, valueZ, and symBols are my vectors.
For some clarification:
The If-Else chain is just used to read instruction words and to set basedInt to the proper decimal number for later hexadecimal conversion.
There are a few special conditions in the code below which are marked.
If there is no special condition then the code checks the valueZ vector at instructions.at(i) to see if the valueZ element is in symBols.
If it is a symBol element through character checks, it takes its hexNums position and adds it to the basedInt.
If it is not, it instead has its corresponding valueZ element converted from string to int and then added to the basedInt.
Those elements are added to the secondPassData vector.
int basedInt;
int newInt;
int pushInt;
string temp;
for(unsigned int i = 0; i < instructions.size(); ++i) //if i is less then instructions.size(), follow through with the statement
{
if(instructions.at(i) == "JNS") //sets basedInt to a decimal version of its hexidecimal opcode
{
basedInt = 0;
}
else if(instructions.at(i) == "HALT") //a special condition where the number is plugged into the secondPassData vector automatically
{
secondPassData.push_back(28672);
continue;
}
else if(instructions.at(i) == "CLEAR") //same as above
{
secondPassData.push_back(-24576);
continue;
}
else if(instructions.at(i) == "ADDL")
else if(instructions.at(i) == "ORG")
{
secondPassData.push_back(0000);
continue;
}
else if(instructions.at(i) == "HEX") //checks for the HEX psuedo-OP.
{
temp = valueZ.at(i); //converts it at position i to a string
basedInt = atoi(temp.c_str()); //converts that string to an int.
secondPassData.push_back(basedInt);//pushes into vector.
continue;
}
else if(instructions.at(i) == "DEC")
{
temp = valueZ.at(i);
basedInt = atoi(temp.c_str()); //similar function as above.
secondPassData.push_back(basedInt);
continue;
}
else
{
cout << "Beep Boop, program borked!" << endl;
return;
}
//for some reason the code below is getting ignored.
cout << i << endl;
for(unsigned int a = 0; a < instructions.size(); ++a) //works
{
cout << i << " " << a << endl;
string valFind = valueZ.at(i);
string symFind = symBols.at(a); //works
temp = valueZ.at(i);
if(symFind[0] == valFind[0])
{
newInt = hexNums.at(a);
pushInt = basedInt + newInt;
secondPassData.push_back(pushInt);
break;
}
else if(symFind[0] != valFind[0]) //works
{
temp = valueZ.at(i);
newInt = atoi(temp.c_str()); //works
pushInt= basedInt + newInt;
secondPassData.push_back(pushInt); //works
break;
}
break;
}
}
If you hit a continue in your else-if chain your main for loop will jump to its next iteration and will skip the rest of your code (in this case your nested for loop)
continue