題目:
有一棵二叉樹,請設計一個算法,按照層次打印這棵二叉樹。給定二叉樹的根結點root,請返回打印結果,結果按照每一層一個數組進行儲存,所有數組的順序按照層數從上往下,且每一層的數組內元素按照從左往右排列。保證結點數小於等於500。
解析:
代碼:
import java.util.*;
/*
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;
public TreeNode(int val) {
this.val = val;
}
}*/
public class TreePrinter {
public int[][] printTree(TreeNode root) {
// write code here
TreeNode last, nlast;
Vector<Vector<Integer>> vec = new Vector<Vector<Integer>>();
if (root == null){
return null;
}
last = nlast = root;
LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
queue.add(root);
TreeNode node = null;
Vector<Integer> v = new Vector<Integer>();
while(!queue.isEmpty()){
node = queue.poll();
if(null != node.left){
nlast = node.left;
queue.add(node.left);
}
if(null != node.right){
nlast = node.right;
queue.add(node.right);
}
v.add(node.val);
if(node == last){
last = nlast;
vec.addElement(v);
v = new Vector<Integer>();
}
}
int[][] result = new int[vec.size()][];
int len;
for(int i =0; i < vec.size(); i++){
len = vec.get(i).size();
result[i] = new int[len];
for(int j = 0; j < len; j++)
result[i][j] = vec.get(i).get(j);
}
return result;
}
}