Coloring Edges（有向图环染色）-- Educational Codeforces Round 72 (Rated for Div. 2)

题意：https://codeforc.es/contest/1217/problem/D

给你一个有向图，要求一个循环里不能有相同颜色的边，问你最小要几种颜色染色，怎么染色？

思路：

如果没有环，那全是1；如果有环，那小到大的边为1，大到小的边为2。

#define IOS ios_base::sync_with_stdio(0); cin.tie(0);
#include <cstdio>//sprintf islower isupper
#include <cstdlib>//malloc  exit strcat itoa system("cls")
#include <iostream>//pair
#include <fstream>//freopen("C:\Users\13606\Desktop\草稿.txt","r",stdin);
#include <bitset>
//#include <G>
//#include<unordered_map>
#include <vector>
#include <stack>
#include <set>
#include <string.h>//strstr substr
#include <string>
#include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
#include <cmath>
#include <deque>
#include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
#include <vector>//emplace_back
//#include <math.h>
//#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
#include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
#define fo(a,b,c) for(register int a=b;a<=c;++a)
#define fr(a,b,c) for(register int a=b;a>=c;--a)
#define mem(a,b) memset(a,b,sizeof(a))
#define pr printf
#define sc scanf
#define ls rt<<1
#define rs rt<<1|1
typedef long long ll;
void swapp(int &a,int &b);
double fabss(double a);
int maxx(int a,int b);
int minn(int a,int b);
int Del_bit_1(int n);
int lowbit(int n);
int abss(int a);
//const long long INF=(1LL<<60);
const double E=2.718281828;
const double PI=acos(-1.0);
const int inf=(1<<30);
const double ESP=1e-9;
const int mod=(int)1e9+7;
const int N=(int)1e6+10;

int in[N];
vector<vector<int> > G(N);

bool top_sort(int n)
{
    int cont=0;
    queue<int> q;
    for(int i=1;i<=n;i++)
        if(in[i]==0)
            q.push(i);
    while(!q.empty())
    {
        int x=q.front();
        q.pop();
        cont++;
        for(int i=0;i<G[x].size();i++)
        {
            in[G[x][i]]--;
            if(in[G[x][i]]==0)
                q.push(G[x][i]);
        }
    }
    return (cont==n);
}
struct node
{
    int u,v;
}edge[N];

int main()
{
    int n,m;
    sc("%d%d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        int u,v;
        sc("%d%d",&u,&v);
        edge[i]={u,v};
        in[v]++;
        G[u].push_back(v);
    }
    if(top_sort(n))
    {
        pr("1
");
        for(int i=1;i<=m;++i)
            pr("1 ");
    }
    else
    {
        pr("2
");
        for(int i=1;i<=m;++i)
            pr("%d ",edge[i].u>edge[i].v?1:2);
    }
    return 0;
}

/**************************************************************************************/

int maxx(int a,int b)
{
    return a>b?a:b;
}

void swapp(int &a,int &b)
{
    a^=b^=a^=b;
}

int lowbit(int n)
{
    return n&(-n);
}

int Del_bit_1(int n)
{
    return n&(n-1);
}

int abss(int a)
{
    return a>0?a:-a;
}

double fabss(double a)
{
    return a>0?a:-a;
}

int minn(int a,int b)
{
    return a<b?a:b;
}