Problem p01557 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>

#define _overload(_1, _2, _3, name, ...) name
#define _rep(i, n) _range(i, 0, n)
#define _range(i, a, b) for (int i = int(a); i < int(b); ++i)
#define rep(...) _overload(__VA_ARGS__, _range, _rep, )(__VA_ARGS__)

#define _rrep(i, n) _rrange(i, n, 0)
#define _rrange(i, a, b) for (int i = int(a) - 1; i >= int(b); --i)
#define rrep(...) _overload(__VA_ARGS__, _rrange, _rrep, )(__VA_ARGS__)

#define _all(arg) begin(arg), end(arg)
#define uniq(arg) sort(_all(arg)), (arg).erase(unique(_all(arg)), end(arg))
#define getidx(ary, key) lower_bound(_all(ary), key) - begin(ary)
#define clr(a, b) memset((a), (b), sizeof(a))
#define bit(n) (1LL << (n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template <class T> bool chmax(T &a, const T &b) {
  return (a < b) ? (a = b, 1) : 0;
}
template <class T> bool chmin(T &a, const T &b) {
  return (b < a) ? (a = b, 1) : 0;
}

using ll = long long;
using R = long double;
const R EPS = 1e-9; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R &r) { return (r > EPS) - (r < -EPS); }
inline R sq(R x) { return sqrt(max<R>(x, 0.0)); }

const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};

// Problem Specific Parameter:

int ans = 9;
map<vector<int>, int> memo;

void make(vector<int> &a, int d) {
  const int n = a.size();

  if (memo.find(a) == end(memo))
    memo[a] = d;
  chmin(memo[a], d);

  if (d == 4)
    return;
  rep(j, n) rep(i, j) {
    reverse(begin(a) + i, begin(a) + j + 1);
    make(a, d + 1);
    reverse(begin(a) + i, begin(a) + j + 1);
  }
}

void dfs(vector<int> &a, int d) {
  const int n = a.size();
  if (memo.find(a) != end(memo))
    chmin(ans, d + memo[a]);

  if (d == 4)
    return;
  rep(j, n) rep(i, j) {
    reverse(begin(a) + i, begin(a) + j + 1);
    dfs(a, d + 1);
    reverse(begin(a) + i, begin(a) + j + 1);
  }
}

int main(void) {
  int n;
  cin >> n;

  vector<int> in(n);
  rep(i, n) cin >> in[i];
  make(in, 0);

  vector<int> init(n);
  iota(begin(init), end(init), 1);
  dfs(init, 0);

  cout << ans << endl;
  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T> inline T sqr(T x) { return x * x; }

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;

#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define pb push_back
#define mp make_pair
#define each(i, c)                                                             \\
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define exist(s, e) ((s).find(e) != (s).end())
#define range(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) range(i, 0, n)
#define clr(a, b) memset((a), (b), sizeof(a))
#define dump(x) cerr << #x << " = " << (x) << endl;
#define debug(x)                                                               \\
  cerr << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << endl;

const double eps = 1e-10;
const double pi = acos(-1.0);
const ll INF = 1LL << 62;
const int inf = 1 << 29;

map<vi, int> dist, dist2;

int main(void) {
  int n;
  cin >> n;

  vi in(n, 0);
  rep(i, n) in[i] = i + 1;
  dist[in] = 0;
  queue<vi> q;
  q.push(in);

  while (!q.empty()) {
    vi ci = q.front();
    q.pop();
    rep(i, n) rep(j, n) {
      if (j + 1 - i <= 1)
        continue;
      vi ni = ci;
      reverse(ni.begin() + i, ni.begin() + j + 1);
      if (dist.find(ni) == dist.end()) {
        if (dist[ci] > 3)
          continue;
        dist[ni] = dist[ci] + 1;
        q.push(ni);
      }
    }
  }

  vi in2(n, 0);
  rep(i, n) cin >> in2[i];
  dist2[in2] = 0;
  q.push(in2);

  while (!q.empty()) {
    vi ci = q.front();
    q.pop();
    rep(i, n) rep(j, n) {
      if (j + 1 - i <= 1)
        continue;
      vi ni = ci;
      reverse(ni.begin() + i, ni.begin() + j + 1);
      if (dist2.find(ni) == dist2.end()) {
        if (dist2[ci] > 3)
          continue;
        dist2[ni] = dist2[ci] + 1;
        q.push(ni);
      }
    }
  }

  int ans = n - 1;
  for (auto &i : dist) {
    if (dist2.find(i.first) == dist2.end())
      continue;
    ans = min(ans, dist[i.first] + dist2[i.first]);
  }
  cout << ans << endl;
  return 0;
}