Problem p01423 (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 DEBUG

#ifdef DEBUG
#define dump(...) fprintf(stderr, __VA_ARGS__)
#else
#define dump(...)
#endif

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 namespace std;
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;

const double EPS = 1e-10;
const double PI = acos(-1.0);
const int inf = 1LL << 30;
const ll mod = 1000000007LL;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll extgcd(ll a, ll b, ll &x, ll &y) {
  x = 1, y = 0;
  ll g = a;
  if (b != 0)
    g = extgcd(b, a % b, y, x), y -= a / b * x;
  return g;
}
ll ADD(const ll &a, const ll &b, const ll &mod) { return (a + b) % mod; }
ll SUB(const ll &a, const ll &b, const ll &mod) { return (a - b + mod) % mod; }
ll MUL(const ll &a, const ll &b, const ll &mod) { return (1LL * a * b) % mod; }
ll DIV(const ll &a, const ll &b, const ll &mod) {
  ll x, y;
  extgcd(b, mod, x, y);
  return MUL(a, (x + mod) % mod, mod);
}

random_device rd;
mt19937 mt(rd());
uniform_int_distribution<int> dice(1, 6);
uniform_real_distribution<double> score(0.0, 10.0);

int n, res;
using vvi = vector<vi>;
vvi costs;
vi invited, used;

void dfs(int v) {
  if (v == n) {
    int cost = 0;
    rep(i, n) {
      if (not invited[i])
        continue;

      int diff = inf;
      rep(j, n) {
        if (i != j and invited[j]) {
          chmin(diff, costs[i][j]);
        }
      }
      if (diff == inf)
        continue;

      cost += diff;
    }
    chmax(res, cost);

    return;
  }

  // not use v
  dfs(v + 1);

  if (used[v])
    return;

  // use v
  invited[v] = true;
  vi idxs;
  rep(u, v + 1, n) {
    if (costs[v][u] == 0 and not used[u]) {
      used[u] = true;
      idxs.push_back(u);
    }
  }
  dfs(v + 1);
  for (auto &u : idxs) {
    used[u] = false;
  }
  invited[v] = false;
}

int main(void) {
  int m;
  cin >> n >> m;
  costs = vvi(n, vi(n));

  rep(loop, m) {
    int a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    costs[a][b] = costs[b][a] = c;
  }

  invited = used = vi(n);
  res = 0;
  dfs(0);

  cout << res << endl;

  return 0;
}

Error: TLE

Fixed submission:

#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 DEBUG

#ifdef DEBUG
#define dump(...) fprintf(stderr, __VA_ARGS__)
#else
#define dump(...)
#endif

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 namespace std;
using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;

const double EPS = 1e-10;
const double PI = acos(-1.0);
const int inf = 1LL << 30;
const ll mod = 1000000007LL;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll extgcd(ll a, ll b, ll &x, ll &y) {
  x = 1, y = 0;
  ll g = a;
  if (b != 0)
    g = extgcd(b, a % b, y, x), y -= a / b * x;
  return g;
}
ll ADD(const ll &a, const ll &b, const ll &mod) { return (a + b) % mod; }
ll SUB(const ll &a, const ll &b, const ll &mod) { return (a - b + mod) % mod; }
ll MUL(const ll &a, const ll &b, const ll &mod) { return (1LL * a * b) % mod; }
ll DIV(const ll &a, const ll &b, const ll &mod) {
  ll x, y;
  extgcd(b, mod, x, y);
  return MUL(a, (x + mod) % mod, mod);
}

random_device rd;
mt19937 mt(rd());
uniform_int_distribution<int> dice(1, 6);
uniform_real_distribution<double> score(0.0, 10.0);

int n, res;
using vvi = vector<vi>;
vvi costs;
vi invited, used;

void dfs(int v) {
  if (v == n) {
    int cost = 0;
    rep(i, n) {
      if (not invited[i])
        continue;

      int diff = inf;
      rep(j, n) {
        if (i != j and invited[j]) {
          chmin(diff, costs[i][j]);
        }
      }
      if (diff == inf)
        continue;

      cost += diff;
    }
    chmax(res, cost);

    return;
  }

  // not use v
  dfs(v + 1);

  // use v
  invited[v] = true;
  vi idxs;
  rep(u, v + 1, n) {
    if (costs[v][u] == 0 and not used[u]) {
      used[u] = true;
      idxs.push_back(u);
    }
  }
  dfs(v + 1);
  for (auto &u : idxs) {
    used[u] = false;
  }
  invited[v] = false;
}

int main(void) {
  int m;
  cin >> n >> m;
  costs = vvi(n, vi(n));

  rep(loop, m) {
    int a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    costs[a][b] = costs[b][a] = c;
  }

  invited = used = vi(n);
  res = 0;
  dfs(0);

  cout << res << endl;

  return 0;
}