题目描述
输入两棵二叉树A,B,判断B是不是A的子结构。(ps:我们约定空树不是任意一个树的子结构)
分析
要查找树A中是否存在和树B结构一样的子树,可分成两步:
第一步在树A中找到和B的根节点的值一样的结点N,其实就是树的遍历
第二步再判断树A中以N为根结点的子树是不是包含和树B一样的结构
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
bool HasSubtree(TreeNode* pRoot1, TreeNode* pRoot2)
{
bool result = false;
if (pRoot1 != NULL && pRoot2 != NULL) {
if(pRoot1->val == pRoot2->val)
result = DoesTree1HaveTree2(pRoot1, pRoot2);
if(!result)
result = HasSubtree(pRoot1->left, pRoot2);
if(!result)
result = HasSubtree(pRoot1->right, pRoot2);
}
return result;
}
bool DoesTree1HaveTree2(TreeNode* pRoot1, TreeNode* pRoot2)
{
if (pRoot2 == NULL)
return true;
if (pRoot1 == NULL)
return false;
if (pRoot1->val != pRoot2->val)
return false;
return DoesTree1HaveTree2(pRoot1->left, pRoot2->left) && DoesTree1HaveTree2(pRoot1->right, pRoot2->right);
}
};