c_cpp 15puzzle-iddfs.cpp

Posted 2021-05-14

#include <iostream>
#include <vector>
#include <stack>
#define N 4
#define N2 16
#define MAX_DEPTH 45
using namespace std;

class game{
  public:
  int b[N2];
  int depth;
  int last_move;
  int empty_space;
};
game start;

bool complete(game &g){
  for(int i=0;i<N2;i++){
    if(g.b[i]!=i+1) return false;
  }
  return true;
}

bool dfs(int depth){
  stack<game> s;
  s.push(start);
  while(!s.empty()){
    game g = s.top(); s.pop();
    if(g.depth==depth){
      if(complete(g)) return g.depth;
      continue;
    }
    
    int w=g.empty_space;
    vector<int> move;
    if(w%N>0  ) move.push_back(-1);
    if(w%N<N-1) move.push_back(1);
    if(w/N>0  ) move.push_back(-N);
    if(w/N<N-1) move.push_back(N);

    for(int i:move){
      if(i==-g.last_move) continue;
      game n=g;
      swap(n.b[w],n.b[w+i]);
      n.depth++;
      n.last_move=i;
      n.empty_space=w+i;
      s.push(n);
    }
  }
  return false;
}

int solve(){
  for(int i=0;i<MAX_DEPTH;i++){
    if(dfs(i)) return i;
  }
  return -1;
}

int main(){
  for(int i=0;i<N2;i++){
    int tmp; cin>>tmp;
    if(tmp==0){
      start.b[i]=N2;
      start.empty_space=i;
    }else{
      start.b[i]=tmp;
    }
  }
  start.depth=0;
  start.last_move=0;

  cout<<solve()<<endl;
}