[프로그래머스 3] 단어 변환 (C/C++)

#include <string>
#include <vector>
#include <queue>
#include <map>
using namespace std;
 
vector<string> copy_words;
string copy_target;
 
queue<string> q;
map<string, int> visited;
 
int check(string word, string next)
{
    int cnt = 0;
    
    for(int i = 0; i < word.size(); i++)
    {
        if(word[i] != next[i])
        {
            cnt++;
        }
    }
    
    if(cnt == 1)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}
 
void BFS(string begin)
{
    visited[begin] = 1;
    q.push(begin);
    
    while(!q.empty())
    {
        string word = q.front();
        q.pop();
        
        if(word == copy_target)
        {
            return;
        }
        
        for(int i = 0; i < copy_words.size(); i++)
        {
            if(check(word, copy_words[i]) == 1 && visited[copy_words[i]] == 0)
            {
                visited[copy_words[i]] = visited[word] + 1;
                q.push(copy_words[i]);
            }         
        }     
    } 
}
 
int solution(string begin, string target, vector<string> words)
{
    copy_words = words;
    copy_target = target;
    
    BFS(begin);
    
    if(visited[target] == 0)
    {
        return 0;
    }
    else
    {
        return visited[target]-1;   
    }
}