Codeforces Round 558 (Div. 2)
F
Indecisive Taxi Fee
Codeforces
3000
原题
← E→
翻译中…

In the city of Capypaland where Kuro and Shiro resides, there are $n$ towns numbered from $1$ to $n$ and there are $m$ bidirectional roads numbered from $1$ to $m$ connecting them. The $i$-th road connects towns $u_i$ and $v_i$. Since traveling between the towns is quite difficult, the taxi industry is really popular here. To survive the harsh competition, each taxi company has to find a distinctive trait for their customers.

翻译中…

Kuro is the owner of a taxi company. He has decided to introduce a new fee model for his taxi brand, where the fee for each ride is not calculated based on the trip length, but on the sum of the prices of the roads traveled. The price for each of the $m$ roads has been decided by Kuro himself.

翻译中…

As of now, the price for the road $i$ is $w_i$ and hence the fee for a taxi ride traveling through roads $e_1, e_2, \ldots, e_k$ is $\sum_{i=1}^k w_{e_i}$.

翻译中…

However, Kuro himself is an indecisive person, so he has drafted $q$ plans to change the road price. Each of the plans will be based on the original prices $w_i$, except for a single road $t_j$, the price of which is changed to $x_j$. Note, that the plans are independent of each other.

翻译中…

Shiro is a regular customer of the Kuro's taxi brand since she uses the taxi to travel from town $1$ to town $n$ every day. Since she's so a regular customer, Kuro decided to show her all his $q$ plans before publishing them to the public. Now, Shiro wants to know the lowest fee she must pay to travel from the town $1$ to the town $n$ for each Kuro's plan.

翻译中…

Input

翻译中…

The first line contains three integers $n$, $m$ and $q$ ($2 \le n \le 2 \cdot 10^5$, $1 \le m, q \le 2 \cdot 10^5$) — the number of towns, the number of roads, and the number of plans that Kuro has drafted respectively.

翻译中…

The $i$-th of the next $m$ contains three integers $u_i$, $v_i$ and $w_i$ ($1 \le u_i, v_i \le n$, $1 \le w_i \le 10^9$, $u_i \ne v_i$) — two endpoints and the original price of the $i$-th road.

翻译中…

It is guaranteed, that there is at least one way to travel from town $1$ to town $n$ using these $m$ bidirectional roads.

翻译中…

Each of the next $q$ lines contains two integers $t_j$ and $x_j$ ($1 \leq t_j \leq m, 1 \leq x_j \leq 10^9$) — the index of the road Kuro has planned to change and its new price respectively.

翻译中…

Output

翻译中…

Print $q$ integers — the lowest fee Shiro must pay to get from town $1$ to town $n$ in each of those $q$ plans.

翻译中…

Note

翻译中…

In the first example, the original overview of Capypaland looks like this, where the number next to each road denotes the original prices of the roads,

翻译中…

image

翻译中…

The overview of the first plan,

翻译中…

image

翻译中…

The lowest fee Shiro must pay in this plan is $4$, which corresponds to the path $1 \rightarrow 4$.

翻译中…

The overview of the second plan,

翻译中…

image

翻译中…

The lowest fee Shiro must pay in this plan is $2$, which corresponds to the path $1 \rightarrow 3 \rightarrow 4$.

翻译中…

The overview of the third plan,

翻译中…

image

翻译中…

The lowest fee Shiro must pay in this plan is $5$, which corresponds to the path $1 \rightarrow 2 \rightarrow 4$.

翻译中…

样例

Input #1
4 5 6
1 2 2
2 4 3
1 4 7
1 3 1
3 4 5
3 4
5 1
3 8
1 4
2 1
3 1
Output #1
4
2
5
6
3
1
InputCopy OutputCopy
Input #2
2 4 4
1 2 2
1 2 3
1 2 4
1 2 5
2 1
3 2
4 3
1 5
Output #2
1
2
2
3
InputCopy OutputCopy
Input #3
2 1 1
1 2 1
1 3
Output #3
3
InputCopy OutputCopy
题目信息
题号
1163F
时间限制
2 s
内存限制
512 MB
标签
数据结构
图论
最短路

题面与样例版权归 Codeforces 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。