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/*
* Quick Find algorithm
*
* Very slow as it uses N^2 time as it needs to access the whole array twice.
*
* If we have a 10^9 union commands on 10^9 objects, we'll need 10^18 operations
* to actually finish the algorithm.
* 30+ years of computer time.
*
* Quadratic algorithms don't scale with technology.
*/
public class QuickFindUF {
private int[] id;
/* Constructor */
public QuickFindUF(int N) {
id = new int[N];
for (int i = 0; i < N; i++)
id[i] = i;
}
/* Are the objects connected */
public boolean connected(int p, int q) {
return id[p] == id[q];
}
/* Connect two objects */
public void union(int p, int q) {
int pid = id[p];
int qid = id[q];
for (int i = 0; i < id.length; i++) {
if (id[i] == pid)
id[i] = qid;
}
}
}
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