Submission #156081

#	Time	Username	Problem	Language	Result	Execution time	Memory
156081		IOrtroiii	전압 (JOI14_voltage)	C++14	100 / 100	173 ms	21080 KiB

voltage

#include <bits/stdc++.h>

using namespace std;

const int N = 100100;

int n, m;
vector<int> g[N];
vector<int> tr[N];
int cnt[N];
int ds[N];
int bad;

void dfs1(int v, int p) {
   for (int u : g[v]) {
   	if (u == p) p = 0;
    else if (ds[u] && ds[u] < ds[v])  {
    	// printf("back edge %d -> %d\n", v, u);
        if ((ds[v] & 1) == (ds[u] & 1)) {
           ++bad;
           cnt[v]++;
           cnt[u]--;
        } else {
           cnt[v]--;
           cnt[u]++;
        }
    } else if (!ds[u]) {
        ds[u] = ds[v] + 1;
        tr[v].emplace_back(u);
        // printf("tree edge %d -> %d\n", v, u);
        dfs1(u, v);
    }
   }
}

void dfs2(int v) {
   for (int u : tr[v]) {
      dfs2(u);
      cnt[v] += cnt[u];
   }
}

int main() {
   scanf("%d %d", &n, &m);
   for (int i = 1; i <= m; ++i) {
      int v, u;
      scanf("%d %d", &v, &u);
      g[v].emplace_back(u);
      g[u].emplace_back(v);
   }
   for (int i = 1; i <= n; ++i) {
      if (!ds[i]) {
         ds[i] = 1;
         dfs1(i, -1);
      }
   }
   for (int i = 1; i <= n; ++i) {
      if (ds[i] == 1) {
         dfs2(i);
      }
   }
   int ans = 0;
   for (int i = 1; i <= n; ++i) {
      if (ds[i] > 1 && cnt[i] == bad) {
         ++ans;
      }
   }
   // printf("%d\n", bad);
   ans += (bad == 1);
   printf("%d\n", ans);
}

Compilation message (stderr)

voltage.cpp: In function 'int main()':
voltage.cpp:44:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d", &n, &m);
    ~~~~~^~~~~~~~~~~~~~~~~
voltage.cpp:47:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
       scanf("%d %d", &v, &u);
       ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 35 / 35
• Subtask 4: 45 / 45