AtCoder Grand Contest 038
D
Unique Path
AtCoder
⌀ 2682
原题
← CE →
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Problem Statement

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Snuke's mother gave Snuke an undirected graph consisting of $N$ vertices numbered $0$ to $N-1$ and $M$ edges. This graph was connected and contained no parallel edges or self-loops.

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One day, Snuke broke this graph. Fortunately, he remembered $Q$ clues about the graph. The $i$-th clue ($0 \leq i \leq Q-1$) is represented as integers $A_i,B_i,C_i$ and means the following:

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  • If $C_i=0$: there was exactly one simple path (a path that never visits the same vertex twice) from Vertex $A_i$ to $B_i$.
  • If $C_i=1$: there were two or more simple paths from Vertex $A_i$ to $B_i$.
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Snuke is not sure if his memory is correct, and worried whether there is a graph that matches these $Q$ clues. Determine if there exists a graph that matches Snuke's memory.

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Constraints

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  • $2 \leq N \leq 10^5$
  • $N-1 \leq M \leq N \times (N-1)/2$
  • $1 \leq Q \leq 10^5$
  • $0 \leq A_i,B_i \leq N-1$
  • $A_i \neq B_i$
  • $0 \leq C_i \leq 1$
  • All values in input are integers.
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Input

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Input is given from Standard Input in the following format:

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N M Q
A_0 B_0 C_0
A_1 B_1 C_1
\vdots
A_{Q-1} B_{Q-1} C_{Q-1}

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Output

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If there exists a graph that matches Snuke's memory, print Yes; otherwise, print No.

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样例

Input #1
5 5 3
0 1 0
1 2 1
2 3 0
Output #1
Yes
For example, consider a graph with edges $(0,1),(1,2),(1,4),(2,3),(2,4)$. This graph matches the clues.
Input #2
4 4 3
0 1 0
1 2 1
2 3 0
Output #2
No
Input #3
10 9 9
7 6 0
4 5 1
9 7 0
2 9 0
2 3 0
4 1 0
8 0 0
9 1 0
3 0 0
Output #3
No
题目信息
题号
agc038_d
时间限制
2 s
内存限制
1024 MB

题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。