Submission #480854

#	Time	Username	Problem	Language	Result	Execution time	Memory
480854		PoPularPlusPlus	Network (BOI15_net)	C++17	100 / 100	495 ms	47756 KiB

net

#include <bits/stdc++.h>
using namespace std;
 
int N;
vector<int> v[500005], ans;
 
void dfs(int x, int p) {
    for(int it : v[x]) {
        if(it == p) continue;
        dfs(it, x);
    }
    if((int)v[x].size() == 1) ans.push_back(x);
}
 
int main() {
    scanf("%d", &N);
    for(int i=1, x, y; i<N; i++) {
        scanf("%d %d", &x, &y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for(int i=1; i<=N; i++) if(v[i].size() > 1) { dfs(i, 0); break; }
    printf("%d\n", (ans.size() + 1) / 2);
    for(int i=0; i<(ans.size() + 1) / 2; i++) printf("%d %d\n", ans[i], ans[i+ans.size()/2]);
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:23:14: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wformat=]
   23 |     printf("%d\n", (ans.size() + 1) / 2);
      |             ~^     ~~~~~~~~~~~~~~~~~~~~
      |              |                      |
      |              int                    std::vector<int>::size_type {aka long unsigned int}
      |             %ld
net.cpp:24:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |     for(int i=0; i<(ans.size() + 1) / 2; i++) printf("%d %d\n", ans[i], ans[i+ans.size()/2]);
      |                  ~^~~~~~~~~~~~~~~~~~~~~
net.cpp:16:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     scanf("%d", &N);
      |     ~~~~~^~~~~~~~~~
net.cpp:18:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |         scanf("%d %d", &x, &y);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 37 / 37