8152: Switch Grass

内存限制:500 MB 时间限制:2 S 标准输入输出
题目类型:传统 评测方式:文本比较 上传者:
提交:6 通过:1

题目描述

Farmer John has recently been experimenting with cultivating different types of grass on his farm, realizing that different types of cows like different types of grass. However, he must be careful to ensure that different types of grass are planted sufficiently far away from each-other, in order to prevent them from being inextricably mixed.

FJ's farm consists of NN fields (1≤N≤200,0001≤N≤200,000), where MM pairs of fields are connected by bi-directional pathways (1≤M≤200,0001≤M≤200,000). Using these pathways, it is possible to walk from any field to any other field. Each pathway has an integer length in the range 1…1,000,0001…1,000,000. Any pair of fields will be linked by at most one direct pathway.

In each field, FJ initially plants one of KK types of grass (1≤K≤N1≤K≤N). Over time, however, he might decide to switch the grass in some field to a different type. He calls this an "update" operation. He might perform several updates over the course of time, which are all cumulative in nature.

After each update, FJ would like to know the length of the shortest path between two fields having different grass types. That is, among all pairs of fields having different grass types, he wants to know which two are closest. Ideally, this number is large, so he can prevent grass of one type from mixing with grass of another type. It is guaranteed that the farm will always have at least two fields with different grass types.

In 30 percent of the input cases, each field will be directly connected to at most 10 pathways.

输入格式

The first line of input contains four integers, NNMMKK, and QQ, where QQ is the number of updates (1≤Q≤200,0001≤Q≤200,000). The next MM lines describe the paths; each one contains three integers AABB, and LL, indicating a path from field AA to field BB (both integers in the range 1…N1…N) of length LL. The next line indicates the initial type of grass growing in each field (NN integers in the range 1…K1…K). Finally, the last QQ lines each describe an update, specified by two integers AA and BB, where the grass in field AA is to be updated to type BB.

输出格式

For each update, print the length of the shortest path between two fields with different types of grass, after the update is applied.

输入样例 复制

3 2 3 4
1 2 3
2 3 1
1 1 2
3 3
2 3
1 2
2 2

输出样例 复制

1
3
3
1