How would I find a partial word match/find c++ - c++

Question

I'm having trouble with a scrabble-like game I'm making. My goal was to have 5 random letters that possibly match at least one word in a dictionary I made so the game can start. I've done this but since the 5 letters are random there's probably a slim chance it will match one of the words in the dictionary. I've done test runs and got random letters but no match every time (it works hardcoded however). I figure if I can find a partial match, I can keep the letter(s) that do form part of a word and get different letters for the ones that don't. The thing is, I don't know how to go about doing this.
This is my code for the five random letters:
void fiveLetters()
{
srand(time(NULL));
for (int i =0; i<=4; i++) // display 5 random letters
{
int n = rand()%26;
char letter = (char)(n+97);
letters[i] = letter;
cout << letters[i]<< " ";
}
letters[5] = '\0'; // last value in char array null value so I can convert to string
attempt = letters; // the 4 letters
checkWords();
}
For checking if it matches a word I use:
void checkWords()
{
if (find(words.begin(),words.end(), attempt) != words.end()) // if matches word in set
{
cout << " Words found" << endl;
}
else // if it doesn't match
{
cout << "cannot find word " << endl;
attempt.clear();
fiveLetters();
}
}
The dictionary is a text file with a lot of words however since I'm just trying to get things working before I implement it, I used 5-10 words and put them in a set<string>. Sorry for the long read, any help is appreciated!

Answer 1

This example demonstrates using a Trie to recursively search for words loaded into it, using search criteria like counts of available letters, minimum word length, and a maximum number of "missing" letters -- letters which are used without being included as an "available" letter.
This Trie is a 26-ary tree, so each node has 26 child nodes, one for each letter in the alphabet. The root node's children are selected using the first letter in a word, the second letter chooses one of this child's children, and so on. A node contains a boolean value indicating that a word ends as that node. Such a node is not a "leaf", however, because the terminated word might be a prefix of a longer word (node terminates "ball", but still has a child branch for "balloon").
The Trie, along with a recursive search is amazingly rapid for your particular task. (By the way, the recursive search doesn't use a recursive function, it stores each level's context on a vector-based stack).
#include <iostream>
#include <string>
#include <unordered_map>
#include <vector>
#include <fstream>
#include <random>
#include <algorithm>
class Trie {
// branch_count defines the number of characters which are combined to make words
// 26 is the number of letters, interpreted case-insensitively
static const int branch_count = 26;
// index_map takes a character and returns a number between 0 and branch_count-1
static int index_map(char c) {
if((c >= 'a') & (c <= 'z')) return c - 'a';
if((c >= 'A') & (c <= 'Z')) return c - 'A';
return -1;
}
// index_unmap takes an index, between 0 and branch_count-1, and returns
// the canonical character representation for that index
static char index_unmap(int index) {
return char('a' + index);
}
// verify_word returns true if all characters in the string map to an index
// returns false if at least one character is not recognized
static bool verify_word(const std::string& word) {
for(auto&& c : word) {
if(index_map(c) == -1) return false;
}
return true;
}
// Node is the Trie's branch_count-ary tree node class
struct Node {
Node* child_nodes[branch_count];
bool terminates_word;
Node() : terminates_word(false) {
for(auto& p : child_nodes) { p = nullptr; }
}
};
// make_lower(str) changes upper-case letters in str to lower-case (in-place)
static void make_lower(std::string& str) {
for(auto& c : str) {
if((c >= 'A') & (c <= 'Z')) {
c += 'a' - 'A';
} } }
// is_space_char(x) returns true when c is some kind of
// unprintable or blank, but nonzero, character
static bool is_space_char(char c) { return (c > 0) & (c <= ' '); }
// trim(str) removes whitespace from the left and right sides
// of str (str is modified in-place)
static void trim(std::string& str) {
const auto len = str.length();
if(!len) return;
auto i = len-1;
if(is_space_char(str[i])) {
for(--i; i+1; --i) {
if(!is_space_char(str[i])) {
str.resize(i+1);
break;
} } }
if(!(i+1)) {
str.clear();
return;
}
i=0;
if(is_space_char(str[i])) {
for(++i;; ++i) {
if(!is_space_char(str[i])) {
str = str.substr(i);
return;
} } } }
Node *root;
int node_count;
int word_count;
public:
// Trie::AddWord(word) stores a string in the Trie
void AddWord(std::string word) {
if(word.empty()) return;
make_lower(word);
if(!verify_word(word)) return;
Node *p = root;
for(const auto c : word) {
const int child_index = index_map(c);
if(child_index == -1) {
// verify_word(word) should have caught this.
// Well-behaved, but might use excess memory.
return;
}
Node *pchild = p->child_nodes[child_index];
if(!pchild) {
p->child_nodes[child_index] = pchild = new Node;
++node_count;
}
p = pchild;
}
if(!p->terminates_word) {
p->terminates_word = true;
++word_count;
} }
// LoadWords(input_stream) loads all line-delimited words from
// the stream into the Trie
int LoadWords(std::istream& stream_in) {
const int start_count = word_count;
std::string line;
while(std::getline(stream_in, line)) {
trim(line);
AddWord(line);
}
return word_count - start_count;
}
// LoadWords(filename) loads all line-delimited words from
// the file at the given path
int LoadWords(const std::string& file_path) {
std::ifstream stream_in(file_path.c_str());
return LoadWords(stream_in);
}
// WordCount() returns the number of words loaded so far
int WordCount() const { return word_count; }
// select_type is a helper for specifying iterator behavior
template <bool select_A, typename A, typename B>
struct select_type { typedef A type; };
template <typename A, typename B>
struct select_type<false, A, B> { typedef B type; };
template <bool select_A, typename A, typename B>
using select_type_t = typename select_type<select_A, A, B>::type;
// The iterator class is used for begin() and end(), as a minimal
// implementation compatible with range-based for,
// as well as by the destructor when destroying the
// tree's Node objects.
template <bool is_const=true, bool delete_iter=false>
class iterator {
friend class Trie;
typedef select_type_t<is_const, const Node*, Node*> pnode_t;
struct context {
pnode_t node;
int child_index;
};
std::vector<context> stack;
pnode_t advance() {
for(;;) {
if(stack.empty()) return nullptr;
pnode_t p = stack.back().node;
int &child_index = stack.back().child_index;
while(++child_index < branch_count) {
pnode_t pchild = p->child_nodes[child_index];
if(pchild) {
stack.push_back({pchild, -1});
if(!delete_iter && pchild->terminates_word) return nullptr;
break;
} }
if(stack.back().child_index == branch_count) {
stack.pop_back();
if(delete_iter) return p;
} } }
public:
iterator(pnode_t root) {
stack.push_back({root, -1});
if(!delete_iter) advance();
}
iterator() {}
std::string operator * () const {
if(stack.empty()) return std::string();
std::string word;
for(int i=0; stack[i].child_index != -1; ++i) {
word += index_unmap(stack[i].child_index);
}
return word;
}
iterator& operator ++ () {
advance();
return *this;
}
bool operator != (const iterator& iter) const {
if(stack.size() != iter.stack.size()) return true;
const int size = static_cast<int>(stack.size());
for(int i=0; i<size; ++i) {
if(stack[i].node != iter.stack[i].node) return true;
}
return false;
}
};
// ctor
Trie() : root(new Node), node_count(1), word_count(0) {}
// dtor
~Trie() {
iterator<false, true> iter(root);
int count = 0;
while(auto pn = iter.advance()) {
delete pn;
++count;
}
//std::cout << "Final word count: " << word_count << '\n';
//std::cout << count << " of " << node_count << " Node objects deleted\n";
}
// const_iterator defined from iterator with template parameter
// for selecting const Node pointers
typedef iterator<true> const_iterator;
const_iterator begin() const { return const_iterator(root); }
const_iterator end() const { return const_iterator(); }
// FindWords:
// * takes an unordered map with char keys and int values
// (counts[ch] = <how many ch may be used>)
// * takes a "max_missing" count (number of substituted characters which
// may be used when none remain in "counts")
// * takes a "min_length", the minimum length a word
// must have to be added to the results
std::vector<std::string> FindWords(const std::unordered_map<char, int>& counts, int max_missing=0, int min_length=0) {
struct context {
const Node* node;
int child_index;
std::unordered_map<char, int> counts;
int missing_count;
bool missing_letter;
context(const Node* node, const std::unordered_map<char, int>& counts, int missing_count) :
node(node),
child_index(-1),
counts(counts),
missing_count(missing_count),
missing_letter(false)
{}
};
std::vector<context> stack;
stack.push_back(context(root, counts, 0));
std::vector<std::string> match_list; // results are added to this
// This walks the tree just like the iterator's advance() function
// however, this function's context includes more info, like
// each level's available letter counts and whether a letter
// was used by taking one of the available "missing" letters.
while(!stack.empty()) {
context& ctx = stack.back();
while(++ctx.child_index < branch_count) {
const Node* pchild = ctx.node->child_nodes[ctx.child_index];
if(!pchild) continue;
const char c = index_unmap(ctx.child_index);
if(ctx.counts[c] > 0) {
ctx.missing_letter = false;
context child_ctx(pchild, ctx.counts, ctx.missing_count);
--child_ctx.counts[c];
stack.push_back(child_ctx); // ctx made invalid here
break;
}
else if(ctx.missing_count < max_missing) {
ctx.missing_letter = true;
context child_ctx(pchild, ctx.counts, ctx.missing_count + 1);
stack.push_back(child_ctx); // ctx made invalid here
break;
} }
context& fresh_ctx = stack.back();
if(fresh_ctx.child_index == branch_count) {
stack.pop_back();
continue;
}
// After a new level is pushed on the stack, check if the last node
// completes a word from the tree, then check various conditions
// required for adding it to the results.
if(static_cast<int>(stack.size()) > min_length && fresh_ctx.node->terminates_word) {
std::string word;
for(const auto& entry : stack) {
if(entry.child_index != -1) {
char c = index_unmap(entry.child_index);
if(entry.missing_letter) {
// modify the character to show it was substituted
if(c >= 'a' && c <= 'z') {
// capitalize missing lower-case letters
word += c + 'A' - 'a';
} else {
// put funky square brackets around other types of missing characters
word += '[';
word += c;
word += ']';
}
} else {
word += c;
} } }
match_list.push_back(word);
} }
return match_list;
}
// FindWords(letters, max_missing, min_length) creates a "counts" map
// from the "letters" string and uses it to call FindWords(counts...)
std::vector<std::string> FindWords(std::string letters, int max_missing=0, int min_length=0) {
std::unordered_map<char, int> counts;
for(auto c : letters) {
switch(c) {
case '?': ++max_missing; break; // '?' is a wildcard (blank tile)
default: ++counts[c]; break;
} }
return FindWords(counts, max_missing, min_length);
}
// DumpAllWords dumps all words contained in the Trie to cout (in alphabetical order)
void DumpAllWords() {
for(auto&& s : *this) {
std::cout << s << '\n';
} }
};
class DrawPool {
std::mt19937 rng;
std::string letters;
int last_count = 1;
struct arg_is_int { char i[4]; };
static arg_is_int argtype(int);
static char argtype(char);
void Add() {}
template <typename T, typename ...Args>
void Add(T arg, Args ...args) {
if(sizeof(argtype(arg)) == sizeof(arg_is_int)) {
last_count = arg;
} else {
letters += std::string(last_count, arg);
}
Add(args...);
}
public:
void Shuffle() {
letters.clear();
Add(2, '?',
12,'e', 9, 'a', 'i', 8, 'o', 6, 'n', 'r', 't',
4, 'l', 's', 'u', 'd', 3, 'g',
2, 'b', 'c', 'm', 'p', 'f', 'h', 'v', 'w', 'y',
1, 'k', 'j', 'x', 'q', 'z');
std::shuffle(letters.begin(), letters.end(), rng);
}
int Count() const { return static_cast<int>(letters.length()); }
std::string Get(int count) {
if(count > Count()) count = Count();
const std::string draw = letters.substr(0, count);
letters.erase(0, count);
return draw;
}
DrawPool() {
std::random_device rd;
std::seed_seq seed = {rd(), rd(), rd(), rd(), rd()};
rng.seed(seed);
Shuffle();
}
};
int main() {
Trie trie;
// Call trie.LoadWords(filename) with each filename in the list
// The names here are files from the SCOWL word lists.
// These may be replaced with your own file name(s).
for(auto s : {
"english-words.10",
"english-words.20",
"english-words.35",
"english-words.40",
"english-words.50",
"english-words.55",
"english-words.60",
"english-words.70",
"english-words.80",
"english-words.95"
}) {
int count = trie.LoadWords(s);
std::cout << "Loaded " << count << " new words from " << s << '\n';
}
std::cout << "\nLoaded a total of " << trie.WordCount() << " words\n";
//trie.DumpAllWords(); // send all words to cout
// match a set of 7 randomly-drawn letters
// draw one more letter each time no matches found
DrawPool draw_pool;
std::string rack;
std::vector<std::string> word_list;
do {
rack += draw_pool.Get(rack.empty() ? 7 : 1);
std::cout << "\nRack: " << rack << '\n';
// find words at least 3 letters long, using the letters
// from "rack". The only "missing" matches allowed are
// 1 for each wildcard ('?') in "rack".
word_list = trie.FindWords(rack, 0, 3);
} while(word_list.empty() && draw_pool.Count());
// Dump the results to cout
std::cout << "\nFound " << word_list.size() << " matches\n";
for(auto&& word : word_list) {
std::cout << " " << word << '\n';
}
}

Answer 2

This is something from my class
if (Variable_name.find(thing to check for) != string::npos)
example
if (myname.find(james) != string::npos)
{
found=true;
//do something
}