union-find算法——使用路径压缩的加权quick-union算法实现

上篇文章union-find算法的使用路径压缩的加权quick-union算法实现

路径压缩就是说在find函数中将所查询触点到根触点所在路径上的所有触点直接连接到根触点上

性能为常数级别

package demo;

public class PathCompressWQU {


/**
* @param args
*/
private int count;
private int[] id;
private int[] sz;

public PathCompressWQU(int n){
count = n;
id = new int[n];
sz = new int[n];
for(int i = 0; i < n; i++){
id[i] = i;
sz[i] =  1;
}
}

public int find(int p){
int temp = p;
while(p != id[p]){
p = id[p];
}

while(temp != id[p]){
int tempId = id[temp];
id[temp] = id[p];
temp = tempId;
}

return id[p];
}

public boolean connect(int p, int q){
return find(p) == find(q);
}

public void union(int p, int q){
int pRoot = find(p);
int qRoot = find(q);

if(pRoot == qRoot) return;

if(sz[pRoot] < sz[qRoot]){
id[pRoot] = id[qRoot];
sz[qRoot] += sz[pRoot];
}
else{
id[qRoot] = id[pRoot];
sz[pRoot] += sz[qRoot];
}

count--;
}

public static void main(String[] args) {
// TODO Auto-generated method stub

int n = StdIn.readInt();


PathCompressWQU pcwqu = new PathCompressWQU(n);
while(!StdIn.isEmpty()){
int p = StdIn.readInt();
int q = StdIn.readInt();

if(pcwqu.connect(p, q)) continue;

pcwqu.union(p, q);

StdOut.println(p + " " + q);
  }

StdOut.println(pcwqu.count + "components");
}


}