Submission #23243

#	Time	Username	Problem	Language	Result	Execution time	Memory
23243		jjwdi0	Network (BOI15_net)	C++11	100 / 100	649 ms	42508 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:23:40: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=]
     printf("%d\n", (ans.size() + 1) / 2);
                                        ^
net.cpp:24:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<(ans.size() + 1) / 2; i++) printf("%d %d\n", ans[i], ans[i+ans.size()/2]);
                   ^
net.cpp:16:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &N);
                    ^
net.cpp:18:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &x, &y);
                               ^

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