Submission #88910

#	Time	Username	Problem	Language	Result	Execution time	Memory
88910		sailormoon	Triumphal arch (POI13_luk)	C++14	100 / 100	1215 ms	39484 KiB

luk

#include <string>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;
int can_handle(int v, int crs, bool visited[]);
vector<vector<int>> graph (1000001); // size

int main() { 
  int n, a, b, start = 0, midpoint, end, cities; // n -> towns, a -> from, b -> to
  scanf("%d", &n);
  end = n; // last point

  for (int i = 1; i < n; i++) {
    scanf("%d %d", &a, &b);
    graph[a].push_back(b);
    graph[b].push_back(a);
  }

  // binary search for sufficient amount of crews
  while (start < end) {
    bool visited[1000001];
    midpoint = (start + end) / 2;
    for (int i = 1; i <= n; i++) visited[i] = false; // clear array 
    if (can_handle(1, midpoint, visited) == 0) end = midpoint;
    else start = ++midpoint; 
  }
  printf("%d\n", start);
  return 0;
}

int can_handle(int v, int crs, bool visited[]) {
  int num_children = 0, need_crews = 0;
  visited[v] = true;
  for (int i = 0; i < graph[v].size(); i++) {
    int cur = graph[v][i];
    if (!visited[cur]) { 
      num_children++;
      need_crews += can_handle(cur, crs, visited);
    }
  }
  if (num_children + need_crews - crs <= 0)
    return 0;
  return num_children + need_crews - crs;
}

Compilation message (stderr)

luk.cpp: In function 'int main()':
luk.cpp:11:42: warning: unused variable 'cities' [-Wunused-variable]
   int n, a, b, start = 0, midpoint, end, cities; // n -> towns, a -> from, b -> to
                                          ^~~~~~
luk.cpp: In function 'int can_handle(int, int, bool*)':
luk.cpp:36:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < graph[v].size(); i++) {
                   ~~^~~~~~~~~~~~~~~~~
luk.cpp: In function 'int main()':
luk.cpp:12:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &n);
   ~~~~~^~~~~~~~~~
luk.cpp:16:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &a, &b);
     ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10