IITWPC4I  Petya and the Road Repairs
Petya is the mayor of a city named Mayapur. In the morning, everybody likes to drink hot tea in bed, and the citizens need milk to take with their tea. For this purpose, they should be able to reach at least some milkman in the city. There are m bidirectional roads in the city but all of them are currently unrepaired, hence not in a state of use.
Petya cares about his city a lot and intends to repair some of these roads, so that every citizen is connected to at least one milkman. For repairing each road he needs to pay a cost. He would like to minimize the cost of this project. Note that a milkman does not need to go to some other milkman for milk as he can take milk from himsaelf.
Help Petya in finding out the minimum cost needed to repair the roads in the given way. If it is not possible for a citizen to connect to any of the milkmen, output "impossible" (without quotes).
Input
The first line contains T: the number of test cases. (1 <= T <= 100)
For each test case, the first line contains two spaceseperated numbers n, m: n is the number of citizens in Mayapur and m denotes the number of unrepaired roads (1 <= n <= 10^5, 1 <= m <= min (n * (n  1) / 2, 2 * 10^5)).
The next line contains n spaceseparated integers, which are either 0 or 1, denoting for successive citizens whether they are a milkman or not.
Then, for each of the next m lines, each line contains three spaceseperated integers u, v and c, denoting that there exists a unrepaired road between u and v such that the cost of repairing of road is c. (1 <= u, v <= n and u != v, 1 <= c <= 10^9.)
Output
For each test case output the cost as required.
Example
Input: 1 5 7 0 1 0 1 0 1 2 11 1 3 1 1 5 17 2 3 1 3 5 18 4 5 3 2 4 5 Output: 5
hide comments
shubham97361:
20190625 19:24:08
tough one....but very good ques. 

sky_scraper:
20190522 08:34:58
Sample case :


abhimanyu_1998:
20190330 02:24:47
Pure DSU , cost we 5 WA because of not printing "impossible" 

marethyu1:
20190321 20:06:03
Use long long int instead of int, it cost me WA. 

ankur2409:
20190318 14:39:47
Nice problem!!! 

jkks1234:
20190110 14:58:35
Distance between 2 nodes can have multiple values take care of that .Thanks @zemotacqy for the test case 

masterchef2209:
20181026 09:32:19
Nice question, all hail kruskal


jeshu123:
20180626 20:06:08
AC in one go!!!! : DSU :) 

techobist:
20180528 06:10:47
A must do problem. It made my day. Try with disjoint sets and you will learn a lot :) 

sdssudhu:
20180523 18:38:05
Classic MST 
Added by:  praveen123 
Date:  20140203 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 
Resource:  IITK ACA CSE online judge 