继上次浅谈了树的遍历之后，这次再浅谈一下树的汇总。此处的汇总是指将树中某节点的数据按指定 的汇集到它的父节点中。例如，可以将树节点中的数值累加到它的父节点中。仍如树的遍历一文，我将使 用两种简单的算法，递归与和迭代，来实现这一功能。(2009.06.26最后更新)
1. 树节点
仍然沿用树的遍历一文中的TreeNode/GenericTreeNode，为便于阅读，将GenericTreeNode中的若干关 键属性展示如下，
public class GenericTreeNode<T> implements TreeNode {
private T userObject = null;
private TreeNode parent = null;
private List<GenericTreeNode<T>> children = new ArrayList<GenericTreeNode<T>>();
}
2. 递归法
仍然先从最简单的递归法开始，
public static Double recursiveGatherValue(GenericTreeNode<Double> node) {
Double sumValue = null;
if (node.isLeaf()) {
return node.getUserObject();
} else {
sumValue = node.getUserObject ();
List<GenericTreeNode<Double>> children = node.getChildren ();
for (int i = 0, size = children.size(); i < size; i++) {
Double bufGatherValue = recursiveGatherValue(children.get(i));
sumValue += bufGatherValue;
}
}
node.setUserObject(sumValue);
return sumValue;
}
递归法还是一如既往的简单易懂。与递归遍历树相比，递归汇总树的程序基本上没大的变化，我就不 赘述了...