LOJ-10108（欧拉回路+并查集）一个图至少用几笔画成

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int maxn = 1001000*2;
int du[maxn],num[maxn],fa[maxn];
int MAX(int x,int y)
{
    return x>y?x:y;
}
int f(int x)
{
    if(fa[x]==0) return x;
    else return fa[x]=f(fa[x]);
}
void Init()
{
    memset(du,0,sizeof(du));
    memset(num,0,sizeof(num));
    memset(fa,0,sizeof(fa));
}
int main(void)
{
    int n,m,t1,t2,i,j,x,y;
    while(~scanf("%d%d",&n,&m)){
        Init();
        for(i=1;i<=m;i++){
            scanf("%d%d",&x,&y);
            du[x]++;du[y]++;
            t1=f(x);t2=f(y);
            if(t1!=t2) fa[t2]=t1;
        }
        for(i=1;i<=n;i++)
        if(du[i]%2) num[f(i)]++;
        
        int cnt=0;
        for(i=1;i<=n;i++)
        if(fa[i]==0&&du[i]) cnt+=MAX(1,num[i]/2);
        printf("%d\n",cnt);
    }
    return 0;
}