I dont know, but if you are using BFS in your solution, you should remember, that graph can contain more than 1 connected component. Try this test:
6
2 3 0
0
0
5 6 0
0
0
one of answers: 011100

Well, I've passed that tests, but still getting WA 13
Any advices?

Why? It works fine for me.

Should be something like:
4
2 0
0
4 0
0

answer 0101 or 0110

try this test

5
2 3 4 5 0
0
0
0
0

the answer should be: 01111

I believe the test is simple. I had WA #8 and the only problem I had I forgot to initialize first vertix to RED color.

Test:
1
0

result:0

If you are anything like me, go get yourself a cup of coffee and then look for a really stupid bug in your dfs.

My program would have failed on the following test:
4
4 0
3 4 0
4 0
0

Input:
4
4 0
3 0
4 0
0

Output:
0101

dfs is enough, but it's better to store graph using compliance matrix, so keeping it in this way, your dfs will visit all nodes (1) and only when current node is already colored (2). If some of node, that we can go fro current is already colored and it has the same color, so -1 should be returned.

So I will answer myself,
This test helped me:
5
2 5 0
3 0
4 0
5 0
0

Maybe it isn't exactly the same test as #6 but i hope that it will help you too.. Good Luck!

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5
2 5 0
3 0
4 0
5 0
0

The above graph (countries forming loop) can help.

Yes, it's correct.

>>The color of the first country is red

int a[10], b[10];
...
cout<<a[15];
...

Such code leads to WA, not Crash, because a[15] is only the address of b[5].