Function add_edge

graph/code8.cpp:11–15

const int inf = 1e9 + 7;

void add_edge(vector<int> vec[], int u, int v)
{
    vec[u].push_back(v);
    vec[v].push_back(u);
}

bool dfs(vector<int> vec[], vector<bool> &visited, int parent, int source)
{