Language: C++

#include <bits/stdc++.h>

#define REP(i, n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()
const int INF = 1e9;

using namespace std;
const int answer[9] = {1, 2, 3, 4, 5, 6, 7, 8, 0};
const int edge[4][3] = {{0, 3, 6}, {0, 1, 2}, {6, 7, 8}, {2, 5, 8}}; /* l, t, b, r */
const bool direction[9][4] = {{false, false, true, true},
                              {true, false, true, true},
                              {true, false, true, false},
                              {false, true, true, true},
                              {true, true, true, true},
                              {true, true, true, false},
                              {false, true, false, true},
                              {true, true, false, true},
                              {true, true, false, false},
                              {true, true, false, false}}
int tiles[9];

int check(){
    int wrongs = 0;
    REP(i, 9)
        if(tiles[i] != answer[i])
            wrongs++;
    return wrongs;
}

int dfs(int moves, int cutoff){
    int wrongs = check();
    if(wrongs == 0)
        return moves;
    if(wrongs + moves > cutoff)
        return -1;
    int zero;
    REP(i, 9){
        if(tiles[i] == 0){
            zero = i;
            break;
        }
    }
    bool dir[4] = dir[zero];
    if(wrongs + moves >= cutoff)
        return -1;
    if(dir[0]){
        swap(tiles[zero], tiles[zero-1]);
        int m = dfs(moves+1, cutoff);
        if(m > 0)
            return m;
        swap(tiles[zero], tiles[zero-1]);
    }
    if(dir[1]){
        swap(tiles[zero], tiles[zero-3]);
        int m = dfs(moves+1, cutoff);
        if(m > 0)
            return m;
        swap(tiles[zero], tiles[zero-3]);
    }
    if(dir[2]){
        swap(tiles[zero], tiles[zero+3]);
        int m = dfs(moves+1, cutoff);
        if(m > 0)
            return m;
        swap(tiles[zero], tiles[zero+3]);
    }
    if(dir[3]){
        swap(tiles[zero], tiles[zero+1]);
        int m = dfs(moves+1, cutoff);
        if(m > 0)
            return m;
        swap(tiles[zero], tiles[zero+1]);
    }
    return -1;
}

int main() {
    REP(i, 9) cin >> tiles[i];
    int move = 0;
    int start = check();

    REP(i, 50){
        move = dfs(0, start + i);
        if(move > 0){
            break;
        }
    }
    cout << move << endl;
    return 0;
}

Compiler output:
a.cc:19:57: error: too many initializers for 'const bool [9][4]'
   19 |                               {true, true, false, false}}
      |                                                         ^
a.cc: In function 'int check()':
a.cc:25:12: error: 'tiles' was not declared in this scope
   25 |         if(tiles[i] != answer[i])
      |            ^~~~~
a.cc: In function 'int dfs(int, int)':
a.cc:38:12: error: 'tiles' was not declared in this scope
   38 |         if(tiles[i] == 0){
      |            ^~~~~
a.cc:43:27: error: array must be initialized with a brace-enclosed initializer
   43 |     bool dir[4] = dir[zero];
      |                   ~~~~~~~~^
a.cc:47:14: error: 'tiles' was not declared in this scope
   47 |         swap(tiles[zero], tiles[zero-1]);
      |              ^~~~~
a.cc:54:14: error: 'tiles' was not declared in this scope
   54 |         swap(tiles[zero], tiles[zero-3]);
      |              ^~~~~
a.cc:61:14: error: 'tiles' was not declared in this scope
   61 |         swap(tiles[zero], tiles[zero+3]);
      |              ^~~~~
a.cc:68:14: error: 'tiles' was not declared in this scope
   68 |         swap(tiles[zero], tiles[zero+1]);
      |              ^~~~~
a.cc: In function 'int main()':
a.cc:78:22: error: 'tiles' was not declared in this scope
   78 |     REP(i, 9) cin >> tiles[i];
      |                      ^~~~~