https://codeforces.com/problemset/problem/216/B

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思路:往环上思考

#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=120;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
bool vis[maxn];
LL col[maxn],tot=0;
vector<LL>g[maxn];
bool flag=1;
void dfs(LL u,LL color){
    vis[u]=1;
    col[u]=color;
    for(LL i=0;i<g[u].size();i++){
        LL v=g[u][i];
        if(col[v]==col[u]){
            flag=0;
            return;
        }
        else if(col[v]!=col[u]&&!vis[v]) dfs(v,color^1);
    }
}
int main(void)
{
  	cin.tie(0);std::ios::sync_with_stdio(false);
    LL n,m;cin>>n>>m;
    memset(col,-1,sizeof(col));
    for(LL i=1;i<=m;i++){
        LL u,v;cin>>u>>v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    LL sum=0;
    for(LL i=1;i<=n;i++){
        if(!vis[i]){
            flag=1;
            tot++;
            dfs(i,1);
            if(flag==0){
                sum+=1;
            }
        }
    }
    if((n-sum)&1) sum++;
    cout<<sum<<"\n";
return 0;
}