Submission #938745

#	Time	Username	Problem	Language	Result	Execution time	Memory
938745		duckindog	경주 (Race) (IOI11_race)	C++17	9 / 100	1327 ms	262144 KiB

race

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
 
using namespace std;
 
#ifndef LOCAL
#include "race.h"
#endif
 
const int N = 200'000 + 1;
vector<pair<int, int>> ad[N];
 
// namespace sub1 {
//   long long d[N];
//   int solve(int n, int k, int l[]) { 
//     for (int i = 1; i < n; ++i) d[i] = d[i - 1] + l[i - 1];
//     int answer = 1e7;
//     for (int i = 1; i < n; ++i) 
//       for (int j = i; j < n; ++j) 
//         if (d[j] - d[i - 1] == k) answer = min(answer, j - i + 1);
      
//     return answer == 1e7 ? -1 : answer; 
//   }
 
// }
 
// namespace sub2 {
//   long long d[N], dep[N];
//   int f[N][10], st[N], ed[N], it;
//   void dfs(int u, int pre = 0) { 
//     st[u] = ++it;
//     for (int i = 1; i <= 9; ++i)
//       f[u][i] = f[f[u][i - 1]][i - 1];
 
//     for (const auto& [v, w] : ad[u]) { 
//       if (v == pre) continue;
//       d[v] = d[u] + w;
//       dep[v] = dep[u] + 1;
//       f[v][0] = u;
//       dfs(v, u);
//     }
//     ed[u] = it;
//   }
//   bool anc(int u, int v) { return st[u] <= st[v] && ed[u] >= ed[v]; }
//   int lca(int u, int v) { 
//     if (anc(u, v)) return u;
//     if (anc(v, u)) return v;
 
//     for (int i = 9; i >= 0; --i)
//       if (!anc(f[u][i], v)) u = f[u][i];
//     return f[u][0];
//   }
 
//   int solve(int n, int k) { 
//     dfs(0);
//     long long answer = 1e7;
//     for (int i = 0; i < n; ++i) { 
//       for (int j = i + 1; j < n; ++j) { 
//         int l = lca(i, j);
//         int distant = d[i] + d[j] - 2 * d[l];
//         if (distant == k) answer = min(answer, dep[i] + dep[j] - 2 * dep[l]);
//       }
//     }
 
//     return answer == 1e7 ? -1 : answer; 
//   }
 
// }
 
namespace sub3 {
  int dpin[N][101], dpout[N][101];
  int n, k;
  void dfs1(int u, int pre = 0) { 
    dpin[u][0] = 0;
    for (const auto& [v, w] : ad[u]) { 
      if (v == pre) continue;
      dfs1(v, u);
      for (int i = 0; i <= k; ++i) { 
        if (i - w >= 0) dpin[u][i] = min(dpin[u][i], dpin[v][i - w] + 1);
      }
    }
  }
 
  void dfs2(int u, int pre = 0) { 
    dpout[u][0] = 0;
    vector<priority_queue<pair<int, int>>> best(k + 1);
    for (const auto&[v, w] : ad[u]) { 
      if (v == pre) continue;
      for (int i = 0; i <= k; ++i) if (i - w >= 0) {
        best[i].push({dpin[v][i - w], v});
        while (best[i].size() > 2) best[i].pop();
      }
    }
    
    for (int i = 0; i <= k; ++i) {
      best[i].push({1e7, -1}); best[i].push({1e7, -1});
      while (best[i].size() > 2) best[i].pop();
    }
    
    for (const auto&[v, w] : ad[u]) { 
      if (v == pre) continue;
      for (int i = 0; i <= k; ++i) { 
        if (i - w < 0) continue;
        int preW = i - w;
        auto top = best[preW].top(); best[preW].pop();
        dpout[v][i] = (best[preW].top().second == v ? top.first : best[preW].top().first) + 2;
        best[preW].push(top);
 
        dpout[v][i] = min(dpout[v][i], dpout[u][i - w] + 1);
      }
      dfs2(v, u);
    }
  }
 
  int solve(int a, int b) { 
    n = a; k = b;
    memset(dpin, 63, sizeof dpin);
    memset(dpout, 63, sizeof dpout);
    dfs1(0); dfs2(0);
    int answer = 1e7;
    for (int i = 0; i <= n; ++i) answer = min({answer, dpin[i][k], dpout[i][k]});
    
    return (answer > n ? -1 : answer);
  }
 
}
 
int best_path(int n, int k, int h[][2], int l[]) { 
  int sub = 1;
  for (int i = 0; i < n - 1; ++i) { 
    int u = h[i][0], v = h[i][1], w = l[i];
    if (u > v) swap(u, v);
    ad[u].push_back({v, w});
    ad[v].push_back({u, w});
    if (u != i || v != i + 1 && sub == 1) sub = 2;
  }
  if (sub > 1) sub = (n <= 1000 ? 2 : k <= 100 ? 3 : 4);
  sub = 3;
  // if (sub == 1) return sub1::solve(n, k, l);
  // if (sub == 2) return sub2::solve(n, k);
  if (sub == 3) return sub3::solve(n, k);
  return -1;
} 
 
#ifdef LOCAL
#define MAX_AA 500000
static int AA, K;
static int H[MAX_AA][2];
static int L[MAX_AA];
static int solution;
 
inline 
void my_assert(int e) {if (!e) abort();}
 
void read_input()
{
  int i;
  my_assert(2==scanf("%d %d",&AA,&K));
  for(i=0; i<AA-1; i++)
    my_assert(3==scanf("%d %d %d",&H[i][0],&H[i][1],&L[i]));
  my_assert(1==scanf("%d",&solution));
}
 
int main()
{
  int ans;
  read_input();
  ans = best_path(AA,K,H,L);
  if(ans==solution)
    printf("Correct.\n");
  else
    printf("Incorrect. Returned %d, Expected %d.\n",ans,solution);
 
  return 0;
}
#endif

Compilation message (stderr)

race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:135:30: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  135 |     if (u != i || v != i + 1 && sub == 1) sub = 2;
      |                   ~~~~~~~~~~~^~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57