二叉树的左视图-java

问题描述：二叉树，从左边看，输出从左边看到的节点。二叉树的左视图

两个java类 

1.TreeNode.java

public class TreeNode {

int val;

TreeNode left;

TreeNode right;

TreeNode(int x){ this.val = x;}

}

 

2.Views.java

public class Views {

 

public void leftSideView(TreeNode root) {

Queue<TreeNode> queue = new LinkedList();

 

queue.add(root);

while (! queue.isEmpty()) {

 

int size = queue.size();

for (int i =0 ;i <size; i++) {

 

TreeNode tempNode = queue.poll();

if (i == 0 ) {

System.out.println(tempNode.val);

}

if (tempNode.left!=null) {

queue.add(tempNode.left);

}

if (tempNode.right!=null) {

queue.add(tempNode.right);

}

}

 

 

}

 

 

}

 

 

 

 

 

 

 

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

TreeNode root = new TreeNode(10);

TreeNode node1  = new  TreeNode(6);

TreeNode node2  = new  TreeNode(20);

TreeNode node3  = new  TreeNode(8);

 

TreeNode node4  = new  TreeNode(15);

 

TreeNode node5  = new  TreeNode(25);

 

TreeNode node6  = new  TreeNode(30);

 

root.left = node1;

root.right = node2;

node1.right = node3;

node2.left= node4;

node2.right = node5;

node5.right = node6;

 

Views views = new Views();

views.leftSideView(root);

 

}

 

 

}