Submission #909902

#	Time	Username	Problem	Language	Result	Execution time	Memory
909902		duckindog	Bridges (APIO19_bridges)	C++14	29 / 100	1130 ms	13476 KiB

bridges

// from duckindog wth depression
#include<bits/stdc++.h>

using namespace std;

#define int long long

const int N = 1e5 + 10;
struct edge {
  int u, v, w;
  edge() : u(0), v(0), w(0) {}
  edge(int u, int v, int w) : u(u), v(v), w(w) {}
} ed[N];
int n, m;
vector<int> ad[N];

int f[N];
int sktra(int x, int mw) {
  memset(f, 63, sizeof f);
  using pii = pair<int, int>;
  priority_queue<pii, vector<pii>, greater<pii>> q;
  q.push({f[x] = 0, x});
  while (q.size()) {
    int d, pre; tie(d, pre) = q.top(); q.pop();
    if (d != f[pre]) continue;
    for (auto i : ad[pre]) {
      int u = ed[i].u, v = ed[i].v, w = ed[i].w;
      if (v == pre) swap(u, v);

      if (f[v] > d + w && w >= mw)
        q.push({f[v] = d + w, v});
    }

  }

  int cnt = 0;
  for (int i = 1; i <= n; ++i) cnt += (f[i] != f[0]);
  return cnt;
}

void sub1() {

  int q; cin >> q;
  while (q--) {
    int ty; cin >> ty;
    if (ty == 1) {
      int i, nw; cin >> i >> nw;
      ed[i].w = nw;

    } else {
      int s, w; cin >> s >> w;

      cout << sktra(s, w) << '\n';

    }

  }

}

int T[4 * N];
void build(int s, int l, int r) {
  if (l == r) {
    T[s] = ed[l].w;
    return;
  }
  int mid = l + r >> 1;
  build(s * 2, l, mid); build(s * 2 + 1, mid + 1, r);
  T[s] = min(T[s * 2], T[s * 2 + 1]);
}
void update(int s, int l, int r, int x, int y) {
  if (y < l || y > r) return;
  if (l == r) {
    T[s] = x;
    return;
  }
  int mid = l + r >> 1;
  update(s * 2, l, mid, x, y); update(s * 2 + 1, mid + 1, r, x, y);
  T[s] = min(T[s * 2], T[s * 2 + 1]);
}
int query(int s, int l, int r, int u, int v) {
  if (v < l || u > r) return 1e9;
  if (u <= l && r <= v) return T[s];
  int mid = l + r >> 1;
  return min(query(s * 2, l, mid, u, v), query(s * 2 + 1, mid + 1, r, u, v));
}

int32_t main() {
  cin.tie(0)->sync_with_stdio(0);

  if (fopen("duck.inp", "r")) {
    freopen("duck.inp", "r", stdin);
    freopen("duck.out", "w", stdout);
  }

  cin >> n >> m;
  bool chain = 1;

  for (int i = 1; i <= m; ++i) {
    int u, v, w; cin >> u >> v >> w;
    ed[i] = {u, v, w};
    ad[u].push_back(i);
    ad[v].push_back(i);
    if (ad[u].size() > 2 || ad[v].size() > 2) chain = 0;
  }

  if (n <= 1e3 && m <= 1e3) {
    sub1();
    return 0;
  }


  if (chain) {
    build(1, 1, m);

    int q; cin >> q;
    while (q--) {
      int ty; cin >> ty;
      if (ty == 1) {
        int i, w; cin >> i >> w;
        update(1, 1, m, w, i);
      } else {
        int i, w; cin >> i >> w;

        int answer = 0;
        int l = 1, r = i - 1, it = i;

        while (l <= r) {
          int mid = l + r >> 1;
          if (query(1, 1, m, mid, i - 1) >= w) r = (it = mid) - 1;
          else l = mid + 1;
        }
        answer += (i - it + 1);

        l = i, r = m, it = i - 1;
        while (l <= r) {
          int mid = l + r >> 1;
          if (query(1, 1, m, i, mid) >= w) l = (it = mid) + 1;
          else r = mid - 1;
        }
        answer += (it - i + 1);

        cout << answer << '\n';
      }

    }

  }


}

Compilation message (stderr)

bridges.cpp: In function 'void build(long long int, long long int, long long int)':
bridges.cpp:67:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   67 |   int mid = l + r >> 1;
      |             ~~^~~
bridges.cpp: In function 'void update(long long int, long long int, long long int, long long int, long long int)':
bridges.cpp:77:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   77 |   int mid = l + r >> 1;
      |             ~~^~~
bridges.cpp: In function 'long long int query(long long int, long long int, long long int, long long int, long long int)':
bridges.cpp:84:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   84 |   int mid = l + r >> 1;
      |             ~~^~~
bridges.cpp: In function 'int32_t main()':
bridges.cpp:129:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  129 |           int mid = l + r >> 1;
      |                     ~~^~~
bridges.cpp:137:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  137 |           int mid = l + r >> 1;
      |                     ~~^~~
bridges.cpp:92:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |     freopen("duck.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
bridges.cpp:93:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   93 |     freopen("duck.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 16 / 16
• Subtask 3: 0 / 17
• Subtask 4: 0 / 14
• Subtask 5: 0 / 13
• Subtask 6: 0 / 27