doublet

#include <iostream>
#include <queue>
#include <stack>
using namespace std;

struct state{
 state* parent;
 char word[16];
};

void result_show(state* tmp){
 if(tmp == NULL)
  return;
 result_show(tmp->parent);
 cout << "use recursive : " << tmp->word << endl;
}

bool doublet(char* a, char* b){
 if(strlen(a) != strlen(b))
  return false;

 int cnt = 0;
 for(int i = 0; i < (int)strlen(a); i++)
  if(a[i] != b[i])
   cnt++;
 if(cnt == 1)
  return true;
 return false;
}

int main(){
 int dic_cnt;
 int testcase_cnt, testcase;
 int i;
 cin >> dic_cnt >> testcase_cnt;

 char** dic = (char**)malloc(sizeof(char*) * dic_cnt);
 for(i = 0; i < dic_cnt; i++){
  dic[i] = (char*)malloc(sizeof(char) * 16);
  cin >> dic[i];
 }

 /*for(i = 0; i < dic_cnt; i++)
  cout << dic[i] << endl;*/
 
 
 for(testcase = 0; testcase < testcase_cnt; testcase++){
  queue<state> openQ, closeQ;
  stack<state> sequence_stack;

  char start_word[16], end_word[16];

  cin >> start_word >> end_word;

  // start state generate

  state start_state;
  start_state.parent = NULL;
  strcpy_s(start_state.word, start_word);

  openQ.push(start_state);

  while(true){
   if(openQ.empty()){
    cout << "No Solution" << endl;
    break;
   }
   state current_state = openQ.front();
   openQ.pop();
   
   if(!strcmp(current_state.word, end_word)){// goal check
    //cout << "goal : " << current_state.word << endl;
    result_show(&current_state);

 

    sequence_stack.push(current_state);
    state* tmp = current_state.parent;
    while(tmp){
     sequence_stack.push(*tmp);
     tmp = tmp->parent;
    }
    
    cout << "goal 1: " << endl;
    while(!sequence_stack.empty()){
     cout << sequence_stack.top().word << endl;
     sequence_stack.pop();
    }
    break;
   }

   // insert current state  to close Q
   closeQ.push(current_state);
   state* current_state_ptr = &closeQ.back();
   // make new state
   for(i = 0; i < dic_cnt; i++){
    if(doublet(current_state.word, dic[i])){ // current state  equal dic's
     if(current_state.parent != NULL){
      if(!strcmp(current_state.parent->word, dic[i]))
       continue;
     }
     state new_state;
     new_state.parent = current_state_ptr;
     strcpy_s(new_state.word, dic[i]);
     openQ.push(new_state);     
    }
   }

  }
 }
}