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 1 /**\
 2 https://codeforces.com/contest/1627/problem/C
 3 想要满足能够赋值的条件,必须所有点的度都不能>3
 4 那么树退化成了链,就op记下输出格式,然后ans记录dfs的结果
 5 由于链式 2 3 2 3 就满足prime path
 6 \**/
 7 #include <bits/stdc++.h>
 8 using namespace std;
 9 #define fi first
10 #define se second
11 #define go continue
12 #define int long long
13 #define PII pair<int, int>
14 #define sf(x) scanf("%lld",&x)
15 #define ytz int _; sf(_); while(_--)
16 #define fory(i,a,b) for(int i = a; i <= b; ++i)
17 #define forl(i,a,b) for(int i = a; i >= b; --i)
18 #define debug(a) cout << #a << " = " << a <<endl;
19 const int N = 1e5 + 10;
20 struct node
21 {
22     int to, next;
23 } e[N << 1];
24 int cnt, head[N];
25 vector<PII> op;
26 map<pair<int, int>, int> ans;
27 int vis[N];
28 int c[N];
29 int n;
30 inline void init()
31 {
32     cnt = 0;
33     fory(i, 0, n) head[i] = -1, c[i] = vis[i] = 0;
34     ans.clear();
35     op.clear();
36 }
37 inline void add_edge(int u, int v)
38 {
39     e[++cnt].to = v;
40     e[cnt].next = head[u];
41     head[u] = cnt;
42     c[v]++;
43 }
44 void dfs(int root, int num)
45 {
46 
47     vis[root] = 1;
48     for(int i = head[root]; ~i; i = e[i].next)
49     {
50         int j = e[i].to;
51         if(!vis[j])
52         {
53             ans[ {root, j}] = ans[ {j, root}] = num;
54             dfs(j, 5 - num);
55         }
56     }
57 }
58 void solve()
59 {
60     sf(n);
61     init();
62     for(int i = 0; i < n - 1; ++i)
63     {
64         int x, y;
65         sf(x), sf(y);
66         add_edge(x, y), add_edge(y, x);
67         op.push_back({x, y});
68     }
69     for(auto t : op)
70     {
71         if(c[t.first] > 2 || c[t.second] > 2)
72         {
73             puts("-1");
74             return;
75         }
76     }
77     fory(i, 1, n)
78     {
79         if(c[i] == 1)
80         {
81             dfs(i, 3);
82             break;
83         }
84     }
85     for(auto t : op)
86     {
87         printf("%lld ", ans[ {t.first, t.second}]);
88     }
89     puts("");
90 }
91 signed main()
92 {
93     ytz
94     {
95         solve();
96     }
97     return 0;
98 }

 

posted @ 2022-03-01 22:25  std&ice  阅读(96)  评论(0)    收藏  举报