问题
判断一棵树是否是另一棵树的子树,如图
思路
问题分两步:
- 找值相同的根结点(遍历解决)
- 判断两结点是否包含(递归:值、左孩子、右孩子分别相同)
树节点定义
struct TreeNode
{
int val;
TreeNode *next;
TreeNode(int v) : val(v), next(NULL) {}
};
代码
bool IsPart(TreeNode *root1, TreeNode *root2)
{
if (root2 == NULL)
return true;
if (root1 == NULL)
return false;
if (root1->val != root2->val)
return false;
return IsPart(root1->left, root2->left) &&
IsPart(root1->right, root2->right);
}
bool IsPartTree(TreeNode *root1, TreeNode *root2)
{
bool result = false;
if (root1 != NULL && root2 != NULL)
{
if (root1->val == root2->val)
result = IsPart(root1, root2);
if (!result)
result = IsPartTree(root1->left, root2);
if (!result)
result = IsPartTree(root1->right, root2);
}
return result;
}
执行
#include <iostream>
#include <stack>
using namespace std;
struct TreeNode
{
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int v) : val(v), left(NULL), right(NULL) {}
};
bool IsPart(TreeNode *root1, TreeNode *root2)
{
if (root2 == NULL)
return true;
if (root1 == NULL)
return false;
if (root1->val != root2->val)
return false;
return IsPart(root1->left, root2->left) &&
IsPart(root1->right, root2->right);
}
bool IsPartTree(TreeNode *root1, TreeNode *root2)
{
bool result = false;
if (root1 != NULL && root2 != NULL)
{
if (root1->val == root2->val)
result = IsPart(root1, root2);
if (!result)
result = IsPartTree(root1->left, root2);
if (!result)
result = IsPartTree(root1->right, root2);
}
return result;
}
TreeNode* createTree1()
{
TreeNode *root = new TreeNode(1);
TreeNode *p1 = new TreeNode(2);
TreeNode *p2 = new TreeNode(3);
TreeNode *p3 = new TreeNode(4);
TreeNode *p4 = new TreeNode(5);
root->left = p1;
root->right = p2;
p2->left = p3;
p2->right = p4;
return root;
}
TreeNode* createTree2()
{
TreeNode *root = new TreeNode(1);
TreeNode *p1 = new TreeNode(2);
TreeNode *p2 = new TreeNode(3);
root->left = p1;
root->right = p2;
return root;
}
void deleteTree(TreeNode *root)
{
if (root != NULL)
{
delete(root->left);
delete(root->right);
delete root;
root = NULL;
}
}
int main()
{
TreeNode *root1 = createTree1();
TreeNode *root2 = createTree2();
cout << IsPartTree(root1, root2) << endl;
deleteTree(root1);
deleteTree(root2);
}
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