Language: C

#include <stdio.h>
#include <stdlib.h>
??
int mas[3][3];
int cpy[3][3];
??
void input() {
????int i, j;
????for(i = 0; i < 3; i++)
????????for(j = 0; j < 3; j++)
????????????scanf("%d", &mas[i][j]);
}
??
void output() {
????int i, j;
????for(i = 0; i < 3; i++) {
????????for(j = 0; j < 3; j++) printf("%3d", mas[i][j]);
????????puts("");
????}
}
??
void copy(int m[3][3], int t[3][3]) {
????int i, j;
??
????for(i = 0; i < 3; i++)
????????for(j = 0; j < 3; j++) m[i][j] = t[i][j];
}
??
int calc() {
????int i, sum = 0;
????for(i = 0; i < 9; i++) {
????????int v = mas[i/3][i%3];
????????if(v) {
????????????v--;
????????????sum += abs(i/3-v/3)+abs(i%3-v%3);
????????}
????}
????return sum;
}
??
int dx[] = {0, 1, 0, -1};
int dy[] = {1, 0, -1, 0};
??
void swap(int *a, int *b) {
????int tmp = *a;
????*a = *b;
????*b = tmp;
}
??
int is_in(int x, int y) {
????return 0<=x&&x<3&&0<=y&&y<3;
}
??
int dfs(int x, int y, int p, int dep, const int lim) {
????int i, h = calc();
????//output();
????if(h == 0) return dep;
????//printf("%d %d %d\n", h, lim, p);
????if(dep+h > lim) return -1;
??
????for(i = 0; i < 4; i++) {
????????int nx = x+dx[i], ny = y+dy[i], res;
????????if(~p && i == (p+2)%4) continue;
????????if(!is_in(nx, ny)) continue;
????????swap(&mas[y][x], &mas[ny][nx]);
????????res = dfs(nx, ny, i, dep+1, lim);
????????if(~res) return res;
????????swap(&mas[y][x], &mas[ny][nx]);
????}
??
????return -1;
}
??
void get_empty(int *x, int *y) {
????int i, j;
????for(i = 0; i < 3; i++) {
????????for(j = 0; j < 3; j++) {
????????????if(!mas[i][j]) {
????????*x = j;
????????*y = i;
????????return;
????????????}
????????}
????}
}
??
int solve() {
????int x, y, lim, ans;
????get_empty(&x, &y);
????for(lim = 0; lim < 50; lim++) {
????????copy(cpy, mas);
????????if((ans = dfs(x, y, -1, 0, lim)) != -1) return ans;
????????copy(mas, cpy);
????}
????return -1;
}
??
int main() {
????input();
????printf("%d\n", solve());
????return 0;
}

Compiler output:
main.c:3:1: error: expected identifier or '(' before '?' token
    3 | ??
      | ^
main.c:6:1: error: expected identifier or '(' before '?' token
    6 | ??
      | ^
main.c:13:1: error: expected identifier or '(' before '?' token
   13 | ??
      | ^
main.c:21:1: error: expected identifier or '(' before '?' token
   21 | ??
      | ^
main.c:28:1: error: expected identifier or '(' before '?' token
   28 | ??
      | ^
main.c:40:1: error: expected identifier or '(' before '?' token
   40 | ??
      | ^
main.c:43:1: error: expected identifier or '(' before '?' token
   43 | ??
      | ^
main.c:49:1: error: expected identifier or '(' before '?' token
   49 | ??
      | ^
main.c:53:1: error: expected identifier or '(' before '?' token
   53 | ??
      | ^
main.c:56:3: warning: trigraph ??/ ignored, use -trigraphs to enable [-Wtrigraphs]
   56 | ????//output();
main.c:58:3: warning: trigraph ??/ ignored, use -trigraphs to enable [-Wtrigraphs]
   58 | ????//printf("%d %d %d\n", h, lim, p);
main.c:73:1: error: expected identifier or '(' before '?' token
   73 | ??
      | ^
main.c:86:1: error: expected identifier or '(' before '?' token
   86 | ??
      | ^
main.c:97:1: error: expected identifier or '(' before '?' token
   97 | ??
      | ^