代码随想录算法训练营DAY14第六章 二叉树 part02

目录

[226. 翻转二叉树](#226. 翻转二叉树)

[101. 对称二叉树](#101. 对称二叉树)

[100. 相同的树](#100. 相同的树)

[572. 另一棵树的子树](#572. 另一棵树的子树)

[104. 二叉树的最大深度](#104. 二叉树的最大深度)

[559. N 叉树的最大深度](#559. N 叉树的最大深度)

[111. 二叉树的最小深度](#111. 二叉树的最小深度)

---

226. 翻转二叉树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(root){
            swap(root->left,root->right);
            invertTree(root->left);
            invertTree(root->right);
        }
        return root;
    }
};

101. 对称二叉树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
    bool com(TreeNode* left, TreeNode* right) {
        if (!left && right)return false;
        else if (left && !right)return false;
        else if (!left && !right)return true;
        else if(left->val!=right->val)return false;
        else return com(left->left,right->right)&&com(left->right,right->left);
    }

public:
    bool isSymmetric(TreeNode* root) {
        if(!root)return true;
        return com(root->left,root->right);
    }
};

100. 相同的树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if(!p&&!q)return true;
        else if(!p||!q)return false;
        if(p->val!=q->val)return false;
        return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);
    }
};

572. 另一棵树的子树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if (!p  || !q ) return p == q;
        return p->val == q->val && isSameTree(p->left, q->left) &&isSameTree(p->right, q->right);
    }

public:
    bool isSubtree(TreeNode* root, TreeNode* subRoot) {
        if (!root) return false;
        return isSameTree(root, subRoot) || isSubtree(root->left, subRoot) ||
               isSubtree(root->right, subRoot);
    }
};

104. 二叉树的最大深度

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(!root)return 0;
        int left=maxDepth(root->left);
        int right=maxDepth(root->right);
        return max(left,right)+1;
    }
};

559. N 叉树的最大深度

/*
// Definition for a Node.
class Node {
public:
    int val;
    vector<Node*> children;

    Node() {}

    Node(int _val) {
        val = _val;
    }

    Node(int _val, vector<Node*> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
public:
    int maxDepth(Node* root) {
        if(!root)return 0;
        int deep=0;
        vector<Node*>c=root->children;
        for(auto child : c){
            int childdeep=maxDepth(child);
            deep=max(deep,childdeep);
        }
        return deep+1;
    }
};

111. 二叉树的最小深度

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode* root) {
        if(!root)return 0;
        if(!root->left&&!root->right)return 1;
        int deep=INT_MAX;
        if(root->left)deep=min(minDepth(root->left),deep);
        if(root->right)deep=min(minDepth(root->right),deep);
        return deep+1;
    }
};