Andryusha and Colored Balloons

dfs记录一下父节点就好了

#include<iostream> #include<cstdio>#include<cstring>#include<vector>using namespace std;int arr[200004];vector<int>u[200004];int m=0;void  dfs(int node ,int father){    int now=1;    for(int e=0;e<u[node].size();e++)    {        int k=u[node][e];        if(arr[k]==-1)        {            while(now==arr[father]||now==arr[node])            now++;            arr[k]=now++;            m=max(m,now-1);            dfs(k,node,father);        }    }}int main(){    memset(arr,-1,sizeof(arr));    int num;    cin>>num;     for(int i=0;i<num-1;i++)    {        int a,b;        scanf("%d%d",&a,&b);        u[a].push_back(b);        u[b].push_back(a);    }    arr[1]=1;    arr[0]=1;    dfs(1,0);    cout<<m<<endl;    for(int i=1;i<=num;i++)    {        if(i!=1)cout<<" "<<arr[i];        else        cout<<arr[i];    }    return 0;}