剑指offer 树的子结构

/**
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

public TreeNode(int val) {
this.val = val;

}

}
*/
public class Solution {
public boolean HasSubtree(TreeNode root1, TreeNode root2) {
boolean result = false;
if (root1 != null && root2 != null) {
if (root1.val == root2.val) {
result = DoesTree1HaveTree2(root1, root2);
}
if (!result) {
result = HasSubtree(root1.left, root2);
}
if (!result) {
result = HasSubtree(root1.right, root2);
}
}
return result;
}

public boolean DoesTree1HaveTree2(TreeNode root1, TreeNode root2) {
if (root2 == null) {
return true;
}
if (root1 == null) {
return false;
}
if (root1.val != root2.val) {
return false;
}
return DoesTree1HaveTree2(root1.left, root2.left) &&
DoesTree1HaveTree2(root1.right, root2.right);
}
}