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。

  1 #define IOS ios_base::sync_with_stdio(0); cin.tie(0);
  2 #include <cstdio>//sprintf islower isupper
  3 #include <cstdlib>//malloc  exit strcat itoa system("cls")
  4 #include <iostream>//pair
  5 #include <fstream>//freopen("C:\\Users\\13606\\Desktop\\草稿.txt","r",stdin);
  6 #include <bitset>
  7 //#include <G>
  8 //#include<unordered_map>
  9 #include <vector>
 10 #include <stack>
 11 #include <set>
 12 #include <string.h>//strstr substr
 13 #include <string>
 14 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
 15 #include <cmath>
 16 #include <deque>
 17 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
 18 #include <vector>//emplace_back
 19 //#include <math.h>
 20 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
 21 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
 22 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
 23 #define fo(a,b,c) for(register int a=b;a<=c;++a)
 24 #define fr(a,b,c) for(register int a=b;a>=c;--a)
 25 #define mem(a,b) memset(a,b,sizeof(a))
 26 #define pr printf
 27 #define sc scanf
 28 #define ls rt<<1
 29 #define rs rt<<1|1
 30 typedef long long ll;
 31 void swapp(int &a,int &b);
 32 double fabss(double a);
 33 int maxx(int a,int b);
 34 int minn(int a,int b);
 35 int Del_bit_1(int n);
 36 int lowbit(int n);
 37 int abss(int a);
 38 //const long long INF=(1LL<<60);
 39 const double E=2.718281828;
 40 const double PI=acos(-1.0);
 41 const int inf=(1<<30);
 42 const double ESP=1e-9;
 43 const int mod=(int)1e9+7;
 44 const int N=(int)1e6+10;
 45 
 46 int in[N];
 47 vector<vector<int> > G(N);
 48 
 49 bool top_sort(int n)
 50 {
 51     int cont=0;
 52     queue<int> q;
 53     for(int i=1;i<=n;i++)
 54         if(in[i]==0)
 55             q.push(i);
 56     while(!q.empty())
 57     {
 58         int x=q.front();
 59         q.pop();
 60         cont++;
 61         for(int i=0;i<G[x].size();i++)
 62         {
 63             in[G[x][i]]--;
 64             if(in[G[x][i]]==0)
 65                 q.push(G[x][i]);
 66         }
 67     }
 68     return (cont==n);
 69 }
 70 struct node
 71 {
 72     int u,v;
 73 }edge[N];
 74 
 75 int main()
 76 {
 77     int n,m;
 78     sc("%d%d",&n,&m);
 79     for(int i=1;i<=m;++i)
 80     {
 81         int u,v;
 82         sc("%d%d",&u,&v);
 83         edge[i]={u,v};
 84         in[v]++;
 85         G[u].push_back(v);
 86     }
 87     if(top_sort(n))
 88     {
 89         pr("1\n");
 90         for(int i=1;i<=m;++i)
 91             pr("1 ");
 92     }
 93     else
 94     {
 95         pr("2\n");
 96         for(int i=1;i<=m;++i)
 97             pr("%d ",edge[i].u>edge[i].v?1:2);
 98     }
 99     return 0;
100 }
101 
102 /**************************************************************************************/
103 
104 int maxx(int a,int b)
105 {
106     return a>b?a:b;
107 }
108 
109 void swapp(int &a,int &b)
110 {
111     a^=b^=a^=b;
112 }
113 
114 int lowbit(int n)
115 {
116     return n&(-n);
117 }
118 
119 int Del_bit_1(int n)
120 {
121     return n&(n-1);
122 }
123 
124 int abss(int a)
125 {
126     return a>0?a:-a;
127 }
128 
129 double fabss(double a)
130 {
131     return a>0?a:-a;
132 }
133 
134 int minn(int a,int b)
135 {
136     return a<b?a:b;
137 }