Submission #253008

#	Time	Username	Problem	Language	Result	Execution time	Memory
253008		Kubin	Race (IOI11_race)	C++17	21 / 100	3109 ms	169080 KiB

race

#include <bits/stdc++.h>

using namespace std;

vector<vector<pair<size_t, int>>> graph;

const int oo = INT_MAX / 3;
int& rd(map<int, int>& m, int key)
{
    auto it = m.find(key);
    if(it == m.end()) it = m.emplace_hint(it, key, +oo);
    return it->second;
}

void mini(map<int, int>& m, int key, int value)
{
    rd(m, key) = min(rd(m, key), value);
}


void dfs_map_paths(size_t u, int s, int d, map<int, int>& m,
                   size_t glock = SIZE_MAX, size_t lock = SIZE_MAX)
{
    if(d > +oo) return;
    mini(m, s, d);
    for(auto [v, w] : graph[u])
        if(v != lock and v != glock)
            dfs_map_paths(v, s + w, d + 1, m, glock, u);
}


size_t find_centroid(size_t init, size_t lock = SIZE_MAX)
{
    (void)lock;
    return init;
}

int solve(size_t init, int k, size_t lock = SIZE_MAX)
{
    auto fix = find_centroid(init, lock);

    int result = +oo;

    map<int, int> pre = {{0, 0}};
    for(auto [v, w] : graph[fix])
      if(v != lock)
    {
        map<int, int> cur;
        dfs_map_paths(v, w, 1, cur, fix);

        for(auto [s, d] : cur)
            result = min(result, d + rd(pre, k - s));
        for(auto [s, d] : cur)
            mini(pre, s, d);
    }

    for(auto [v, w] : graph[fix])
        if(v != lock)
            result = min(result, solve(v, k, fix));

    return result;
}


int best_path(int _n, int k, int H[][2], int L[])
{
    const size_t n = _n;

    graph.resize(n);
    for(size_t i = 0; i < n - 1; i++)
    {
        graph[H[i][0]].emplace_back(H[i][1], L[i]);
        graph[H[i][1]].emplace_back(H[i][0], L[i]);
    }

    int result = solve(0, k);

    return result >= +oo ? -1 : result;
}


#ifdef XHOVA
#define MAX_N 500000

static int N, K;
static int H[MAX_N][2];
static int L[MAX_N];
static int solution;

inline
void my_assert(int e) {if (!e) abort();}

void read_input()
{
  int i;
  my_assert(2==scanf("%d %d",&N,&K));
  for(i=0; i<N-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(N,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 solve(size_t, int, size_t)':
race.cpp:57:19: warning: unused variable 'w' [-Wunused-variable]
     for(auto [v, w] : graph[fix])
                   ^

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