Red-blue Trees SOLUTIONS RBTREES

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Red-blue Trees SOLUTIONS RBTREES

In a red-blue tree, every vertex is either red or blue and contiguous vertices consistently have various hues. 

You are given a tree with N vertices (numbered 1 through N). It isn’t really a red-blue tree, however its vertices are as yet hued red and blue. You may play out the accompanying activity quite a few times (counting zero): pick two nearby vertices and trade their hues. 

Locate the most modest number of tasks needed to change the tree into a red-blue tree or verify that it is inconceivable. 

 

Info 

The main line of the info contains a solitary whole number T indicating the quantity of experiments. The depiction of T experiments follows. 

The main line of each experiment contains a solitary whole number N. N−1 lines follow. Every one of these lines contains two space-isolated numbers u and v signifying that vertices u and v are associated by an edge. 

The last line contains a string S with length N. For each substantial I, the I-th character of this string is either ‘0’ if the I-th vertex is at first red or ‘1’ on the off chance that it is at first blue. 

 

Yield :Print a solitary line containing one whole number ― the most modest number of activities or −1 in the event that it is difficult to change the tree into a red-blue tree. 

 

Requirements 

1≤T≤100 

1≤N≤100,000 

1≤u,v≤N 

S contains just characters ‘0’ and ‘1’ 

the whole of N over all experiments doesn’t surpass 106 

 

Model Input 

1 

7 

1 2 

1 3 

2 4 

2 5 

3 6 

3 7 

0010010 

 

Model Output 

3 

 

Clarification 

Model case 1: We can play out the accompanying activities: 

Trade the shades of vertices 1 and 3; the series of hues becomes “1000010”. 

Trade the shades of vertices 1 and 2; the series of hues becomes “0100010”. 

Trade the shades of vertices 6 and 3; the series of hues becomes “0110000”, so the tree is a red-blue tree..

 

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