Submission #88909

#	Time	Username	Problem	Language	Result	Execution time	Memory
88909		sailormoon	Triumphal arch (POI13_luk)	C++14	100 / 100	1056 ms	39492 KiB

luk

#include <string>
    #include <algorithm>
    #include <iostream>
    #include <vector>
 
    using namespace std;
    int canHandle(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 (canHandle(1, midpoint, visited) == 0) end = midpoint;
        else start = ++midpoint; 
      }
      printf("%d\n", start);
      return 0;
    }
     
    int canHandle(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 += canHandle(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:11:46: 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 canHandle(int, int, bool*)':
luk.cpp:36:25: 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:12:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
       scanf("%d", &n);
       ~~~~~^~~~~~~~~~
luk.cpp:16:14: 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