Submission #839689

#	Time	Username	Problem	Language	Result	Execution time	Memory
839689		Alfraganus	Race (IOI11_race)	C++17	9 / 100	59 ms	16196 KiB

race

#include "race.h"
// #include "grader.cpp"
#include <bits/stdc++.h>
using namespace std;

struct node {
  int sum = 0, node = 0, nodes = 0;
};

int best_path(int n, int k, int h[][2], int l[])
{
    if(n == 1){
      return -1;
    }
    vector<vector<pair<int, int>>> graph(n);
    int root;
    vector<int> cnt(n);
    for(int i = 0; i < n - 1; i ++){
        graph[h[i][0]].push_back({h[i][1], l[i]});
        graph[h[i][1]].push_back({h[i][0], l[i]});
        cnt[h[i][0]] ++;
        cnt[h[i][1]] ++;
    }
    for(int i = 0; i < n; i ++){
      if(cnt[i] == 1){
        root = i;
        break;
      }
    }
    queue<node> q;
    vector<bool> used(n);
    vector<vector<int>> a(n);
    q.push({0, root, 0});
    used[root] = true;
    int ans = 1e7;
    while(!q.empty()){
      node x = q.front();
      q.pop();
      while(x.sum >= k){
        if(x.sum == k)
          ans = min(ans, x.nodes);
        int cur = x.node, y = x.nodes, j = 0, cur1 = x.node;
        while(y){
          if((y & 1))
            cur = a[cur][j];
          y /= 2;
          j ++;
        }
        y = x.nodes - 1;
        j = 0;
        while(y){
          if((y & 1))
            cur1 = a[cur1][j];
          y /= 2;
          j ++;
        }
        for(auto n : graph[cur]){
          if(n.first == cur1){
            x.sum -= n.second;
            break;
          }
        }
        x.nodes --;
      }
      for(auto neighbour : graph[x.node]){
        if(!used[neighbour.first]){
          q.push({x.sum + neighbour.second, neighbour.first, x.nodes + 1});
          used[neighbour.first] = true;
          a[neighbour.first].push_back(x.node);
          for(int i = 1, y = 2; y <= x.nodes + 1; i ++, y <<= 1){
            a[neighbour.first].push_back(a[a[neighbour.first][i - 1]][i - 1]);
          }
        }
      }
    }
    if(ans == 1e7)
      return -1;
    else
      return ans;
}

Compilation message (stderr)

race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:33:11: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   33 |     q.push({0, root, 0});
      |     ~~~~~~^~~~~~~~~~~~~~

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