//https://leetcode.com/problems/graph-valid-tree/
/*
* Approach
* Use Union Find Algorith preferably with weighed quick-union
*
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*/
public bool ValidTree(int n, int[][] edges)
{
WeightedQuickUnionFind qfind = new WeightedQuickUnionFind(n);
int m = edges.GetLength(0);
for (int i = 0; i < m; i++)
{
int p = edges[i][0];
int q = edges[i][1];
//p & q in the same set then there is a cycle
if (qfind.Find(p) == qfind.Find(q))
{
return(false);
}
qfind.Union(p, q);
}
if (qfind.Count() != 1)
{
return(false);
}
return(true);
}
public int RemoveStonesUnionFind(int[][] stones)
{
int L = stones.GetLength(0);
WeightedQuickUnionFind uf = new WeightedQuickUnionFind(L);
for (int i = 0; i < L; i++)
{
for (int j = i + 1; j < L; j++)
{
if (stones[i][0] == stones[j][0] || stones[i][1] == stones[j][1])
{
uf.Union(i, j);
}
}
}
int count = 0;
int[] componentSize = uf.Size(); //calculate the individual component sizes
for (int i = 0; i < componentSize.Length; i++)
{
count += componentSize[i] > 1 ? componentSize[i] - 1 : 0;
}
return(count);
}
