Submission #33887853

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define MOD 1000000007
#define rep(i,a,n) for (ll i=a;i<(ll)n;i++)
#define per(i,a,n) for (ll i=n;i-->(ll)a;)
#define pb push_back

ll read(){ll r;scanf("%lld",&r);return r;} // read

vector<int>p2[200010];

int c[200010]; // count 0

int x(int u){ return c[u] > 0;} // 根据子节点0的个数 推断是否和子节点匹配

void dfs(int u,int f){
  for(auto v:p2[u]) if(v != f) {
    dfs(v,u);
    c[u] += !x(v);
  }
}

void swaproot(int u,int v){
  c[u] -= !x(v);
  c[v] += !x(u);
}

int dfs2(int u,int f){
  int r = !x(u);
  for(auto v:p2[u]) if(v != f) {
    swaproot(u,v);
    r += dfs2(v,u);
    swaproot(v,u);
  }
  return r;
}

int main(){
  int n = read();
  rep(i,1,n){
    int u = read();
    int v = read();
    p2[u].pb(v);
    p2[v].pb(u);
  }
  dfs(1,0);
  printf("%d\n", dfs2(1,0));
  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘ll read()’:
./Main.cpp:10:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   10 | ll read(){ll r;scanf("%lld",&r);return r;} // read
      |                ~~~~~^~~~~~~~~~~

Judge Result