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ScapegoatTree2.java
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48 lines (43 loc) · 973 Bytes
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package ods;
public class ScapegoatTree2<T> extends ScapegoatTree<T> {
protected void rebuild(Node<T> u) {
int n = size(u);
Node<T> p = u.parent;
// FIXME: check if p is root
if (p == nil) {
r = rebuildTree(n,u);
} else if (p.left == u) {
u = rebuildTree(n, u);
p.left = u;
} else {
u = rebuildTree(n, u);
p.right = u;
}
u.parent = p;
}
protected Node<T> flatten(Node<T> x, Node<T> y) {
if (x == nil) return y;
x.right = flatten(x.right, y);
return flatten(x.left, x);
}
protected Node<T> buildTree(int n, Node<T> x) {
if (n == 0) {
x.left = nil;
return x;
}
int k = n/2;
Node<T> r = buildTree(k, x);
Node<T> s = buildTree(n-k-1, r.right);
r.right = s.left;
if (s.left != nil) s.left.parent = r;
s.left = r;
r.parent = s;
return s;
}
protected Node<T> rebuildTree(int n, Node<T> scapegoat) {
Node<T> w = newNode();
Node<T> z = flatten(scapegoat, w);
buildTree(n, z);
return w.left;
}
}