refer to 点击打开链接
- Distance(X, Y) = Distance(root, X) +Distance(root, Y) — 2*(Distance(root to LCA(X,Y)
- where LCA(X,Y) = Lowest Common Ancestor of X,Y
- In the above example if Distance(20,45) = 3
- Distance(root, 20) = 2
- Distance(root, 45) = 3
- LCA(20, 45) = 10
- Distance(root, 10) = 1
- Distance(20,45) = 2+3 — 2*1 = 3
package tree;
public class DistanceTwoNode {
public int findDistance(Node root, int n1, int n2) {
int x = Pathlength(root, n1) - 1;
int y = Pathlength(root, n2) - 1;
int lcaData = findLCA(root, n1, n2).data;
int lcaDistance = Pathlength(root, lcaData) - 1;
return (x + y) - 2 * lcaDistance;
}
public int Pathlength(Node root, int n1) {
if (root != null) {
int x = 0;
if ((root.data == n1) || (x = Pathlength(root.left, n1)) > 0
|| (x = Pathlength(root.right, n1)) > 0) {
// System.out.println(root.data);
return x + 1;
}
return 0;
}
return 0;
}
public Node findLCA(Node root, int n1, int n2) {
if (root == null || root.data == n1 || root.data == n2) {
return root;
}
Node left = findLCA(root.left, n1, n2);
Node right = findLCA(root.right, n1, n2);
if (left != null && right != null) {
return root;
}
if (left != null) {
return left;
}
if (right != null) {
return right;
}
return null;
}
public static void main(String[] args) throws java.lang.Exception {
Node root = new Node(5);
root.left = new Node(10);
root.right = new Node(15);
root.left.left = new Node(20);
root.left.right = new Node(25);
root.right.left = new Node(30);
root.right.right = new Node(35);
root.left.right.right = new Node(45);
DistanceTwoNode i = new DistanceTwoNode();
System.out.println("Distance between 45 and 20 is : "
+ i.findDistance(root, 45, 20));
}
}