AtCoder Beginner Contest 143
E
Travel by Car
AtCoder
⌀ 1695
原题
← DF →
翻译中…

Problem Statement

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There are $N$ towns numbered $1$ to $N$ and $M$ roads. The $i$-th road connects Town $A_i$ and Town $B_i$ bidirectionally and has a length of $C_i$.

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Takahashi will travel between these towns by car, passing through these roads. The fuel tank of his car can contain at most $L$ liters of fuel, and one liter of fuel is consumed for each unit distance traveled. When visiting a town while traveling, he can full the tank (or choose not to do so). Travel that results in the tank becoming empty halfway on the road cannot be done.

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Process the following $Q$ queries:

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  • The tank is now full. Find the minimum number of times he needs to full his tank while traveling from Town $s_i$ to Town $t_i$. If Town $t_i$ is unreachable, print $-1$.
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Constraints

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  • All values in input are integers.
  • $2 \leq N \leq 300$
  • $0 \leq M \leq \frac{N(N-1)}{2}$
  • $1 \leq L \leq 10^9$
  • $1 \leq A_i, B_i \leq N$
  • $A_i \neq B_i$
  • $\left(A_i, B_i\right) \neq \left(A_j, B_j\right)$ (if $i \neq j$)
  • $\left(A_i, B_i\right) \neq \left(B_j, A_j\right)$ (if $i \neq j$)
  • $1 \leq C_i \leq 10^9$
  • $1 \leq Q \leq N\left(N-1\right)$
  • $1 \leq s_i, t_i \leq N$
  • $s_i \neq t_i$
  • $\left(s_i, t_i\right) \neq \left(s_j, t_j\right)$ (if $i \neq j$)
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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 L
A_1 B_1 C_1
:
A_M B_M C_M
Q
s_1 t_1
:
s_Q t_Q

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Output

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Print $Q$ lines.

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The $i$-th line should contain the minimum number of times the tank needs to be fulled while traveling from Town $s_i$ to Town $t_i$. If Town $t_i$ is unreachable, the line should contain $-1$ instead.

翻译中…

样例

Input #1
3 2 5
1 2 3
2 3 3
2
3 2
1 3
Output #1
0
1
To travel from Town $3$ to Town $2$, we can use the second road to reach Town $2$ without fueling the tank on the way. To travel from Town $1$ to Town $3$, we can first use the first road to get to Town $2$, full the tank, and use the second road to reach Town $3$.
Input #2
4 0 1
1
2 1
Output #2
-1
There may be no road at all.
Input #3
5 4 4
1 2 2
2 3 2
3 4 3
4 5 2
20
2 1
3 1
4 1
5 1
1 2
3 2
4 2
5 2
1 3
2 3
4 3
5 3
1 4
2 4
3 4
5 4
1 5
2 5
3 5
4 5
Output #3
0
0
1
2
0
0
1
2
0
0
0
1
1
1
0
0
2
2
1
0
题目信息
题号
abc143_e
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。