我的任务是在二叉树中将节点的值更改为其高度。根据任务的条件,您需要在树的1次传递中更改所有值,但是您可以使用其他数据结构来违反此条件。我有一个代码,但无法正常工作。 This is the original tree,here is what I want to get,and this is the result of the program written below
public void replaceValuesToHeight() {
ArrayDeque<TreeNode> leftTreeQueue = new ArrayDeque<>();
ArrayDeque<TreeNode> rightTreeQueue = new ArrayDeque<>();
rightTreeQueue.add(getRoot());
replaceValuesToHeight(getRoot(), new ArrayDeque<>(), new ArrayDeque<>(), leftTreeQueue, rightTreeQueue, 0, 0, true);
}
public int replaceValuesToHeight(TreeNode node, ArrayDeque<ArrayDeque<TreeNode>> leftTree, ArrayDeque<ArrayDeque<TreeNode>> rightTree, ArrayDeque<TreeNode> leftTreeQueue, ArrayDeque<TreeNode> rightTreeQueue, int maxLeft, int maxRight, boolean isLeft) {
if (node == null) {
leftTree.add(leftTreeQueue);
rightTree.add(rightTreeQueue);
leftTreeQueue.clear();
rightTreeQueue.clear();
return 0;
}
if (isLeft)
leftTreeQueue.add(node);
maxLeft = replaceValuesToHeight(node.getLeft(), leftTree, rightTree, leftTreeQueue, rightTreeQueue, ++maxLeft, maxRight, true);
if (!isLeft)
rightTreeQueue.add(node);
maxRight = replaceValuesToHeight(node.getRight(), leftTree, rightTree, leftTreeQueue, rightTreeQueue, maxLeft, ++maxRight, false);
int depth = 1 + Math.max(maxLeft, maxRight);
if (node == getRoot()) {
leftTree.clear();
rightTree.clear();
}
node.value = depth;
//rightTreeQueue = rightTree.poll();
//leftTreeQueue = leftTree.poll();
if (maxLeft > maxRight) {
int i = 0;
while (!rightTreeQueue.isEmpty()) {
rightTreeQueue.poll().value = maxLeft - i;
i++;
}
//leftTreeQueue.clear();
} else if (maxRight > maxLeft) {
int i = 0;
while (!leftTreeQueue.isEmpty()) {
leftTreeQueue.poll().value = maxRight - i;
i++;
}
//rightTree.clear();
}
return depth;
}
如果TreeNode是
class TreeNode {
int val;
TreeNode left;
TreeNode right;
}
我认为递归解决方案会更好:
static class TreeNode {
int val;
TreeNode left;
TreeNode right;
public TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
@Override
public String toString() {
return toString(1);
}
private String toString(int tabs) {
String indent = Collections.nCopies(tabs, " ").stream().collect(Collectors.joining());
return String.format("%d, %n%sl:%s,%n%sr:%s", val,
indent, left != null ? left.toString(tabs + 1) : "null",
indent, right != null ? right.toString(tabs + 1) : "null");
}
}
public static void main(String[] args) {
TreeNode root = new TreeNode(0,
new TreeNode(0,
new TreeNode(0,
null,
new TreeNode(0,
null,
null)),
null),
new TreeNode(0,
null,
null));
System.out.println(root);
setHeights(root, 0);
System.out.println(root);
}
private static void setHeights(TreeNode node, int h) {
if (node == null) return;
node.val = h;
setHeights(node.left, h + 1);
setHeights(node.right, h + 1);
}
打印:
0,
l:0,
l:0,
l:null,
r:0,
l:null,
r:null,
r:null,
r:0,
l:null,
r:null
0,
l:1,
l:2,
l:null,
r:3,
l:null,
r:null,
r:null,
r:1,
l:null,
r:null