前序遍历二叉树

class TreeNode {
int val;
TreeNode left;
TreeNode right;

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

public class traversal {

public static void main(String[] args) {

TreeNode t = CreateTree();

dfs(t);

}

//深度优先遍历
public static void dfs(TreeNode root) {
if (root == null) {
return;
}

System.out.println(root.val);

dfs(root.left);
dfs(root.right);

}

public static TreeNode CreateTree() {

TreeNode t1 = new TreeNode(1);
TreeNode t2 = new TreeNode(2);
TreeNode t3 = new TreeNode(3);
TreeNode t4 = new TreeNode(4);
TreeNode t5 = new TreeNode(5);
TreeNode t6 = new TreeNode(6);
TreeNode t7 = new TreeNode(7);
TreeNode t8 = new TreeNode(8);
TreeNode t9 = new TreeNode(9);
TreeNode t10 = new TreeNode(10);

t1.left = t2;
t1.right = t3;
t2.left = t4;
t2.right = t5;
t4.left = t7;
t4.right = t8;
t8.right = t10;
t3.left = t6;
t6.left = t9;

return t1;
}
}