Problem p00485 (C++) — buggy submission, verdict: Time Limit Exceeded

//  Shopping in JOI Kingdom.cpp
//  2013/01/06.

#if 1

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for (int i = x; i < n; i++)
template <class T> T RoundOff(T a) { return int(a + .5 - (a < 0)); }
template <class T, class C> void chmax(T &a, C b) {
  if (a < b)
    a = b;
}
template <class T, class C> void chmin(T &a, C b) {
  if (b < a)
    a = b;
}
template <class T, class C> pair<T, C> mp(T a, C b) { return make_pair(a, b); }

const int INF = 1 << 30;

int N, M, K;
int D[3000];
int C[3000][3000];
int used[3000];

int dfs(int pnt) {
  rep(next, N) if (D[next] > D[pnt] + C[pnt][next]) {
    D[next] = D[pnt] + C[pnt][next];
    dfs(next);
  }
}

void dijkstra(int pnt) {
  memset(used, 0, sizeof used);

  while (true) {
    int v = -1;

    rep(u, N) if (!used[u] && (v == -1 || D[u] < D[v])) v = u;

    if (v == -1)
      break;

    used[v] = true;

    rep(u, N) chmin(D[u], D[v] + C[v][u]);
  }
}

int calc(int a, int b, int l) {
  return round(min(a, b) + (l + max(a, b) - min(a, b)) / 2.0);
}

int main() {
  rep(i, 3000) rep(j, 3000) D[i] = C[i][j] = INF;

  cin >> N >> M >> K;

  rep(m, M) {
    int a, b, c;
    cin >> a >> b >> c;

    C[a - 1][b - 1] = C[b - 1][a - 1] = c;
  }

  int s;
  rep(k, K) {
    cin >> s;

    D[s - 1] = 0;
  }

  dijkstra(s - 1);

  int ans = 0;

  rep(a, N) REP(b, a + 1, N) if (C[a][b] < INF)
      chmax(ans, calc(D[a], D[b], C[a][b]));

  cout << ans << endl;
}

#endif

Error: TLE

Fixed submission:

//  Shopping in JOI Kingdom.cpp
//  2013/01/06.

#if 1

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <fstream>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for (int i = x; i < n; i++)
template <class T> T RoundOff(T a) { return int(a + .5 - (a < 0)); }
template <class T, class C> void chmax(T &a, C b) {
  if (a < b)
    a = b;
}
template <class T, class C> void chmin(T &a, C b) {
  if (b < a)
    a = b;
}
template <class T, class C> pair<T, C> mp(T a, C b) { return make_pair(a, b); }

const int INF = 1 << 30;

int N, M, K;
int D[3000];
int C[3000][3000];
int used[3000];

int dfs(int pnt) {
  rep(next, N) if (D[next] > D[pnt] + C[pnt][next]) {
    D[next] = D[pnt] + C[pnt][next];
    dfs(next);
  }
}

void dijkstra(int pnt) {
  memset(used, 0, sizeof used);

  while (true) {
    int v = -1;

    rep(u, N) if (!used[u] && (v == -1 || D[u] < D[v])) v = u;

    if (v == -1)
      break;

    used[v] = true;

    rep(u, N) chmin(D[u], D[v] + C[v][u]);
  }
}

int calc(int a, int b, int l) {
  return round(min(a, b) + (l + max(a, b) - min(a, b)) / 2.0);
}

int main() {
  rep(i, 3000) rep(j, 3000) D[i] = C[i][j] = INF;

  cin >> N >> M >> K;

  rep(m, M) {
    int a, b, c;
    cin >> a >> b >> c;

    C[a - 1][b - 1] = C[b - 1][a - 1] = c;
  }

  rep(k, K) {
    int s;
    cin >> s;

    D[s - 1] = 0;
    dijkstra(s - 1);
  }

  int ans = 0;

  rep(a, N) REP(b, a + 1, N) if (C[a][b] < INF)
      chmax(ans, calc(D[a], D[b], C[a][b]));

  cout << ans << endl;
}

#endif