树的操作.c

struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

// 二叉树的最大深度
int maxDepth(struct TreeNode* root) {
    if (root) {
        int left = 1;
        int right = 1;
        left += maxDepth(root->left);
        right += maxDepth(root->right);
        
        return left > right ? left : right;
    } else {
        return 0;
    }
}

bool isValidBST(struct TreeNode* root) {
    if (!root) {
        return true;
    } else {
//        int left = lef
        return isValidBST(root->left) && isValidBST(root->right);
    }
    
    
    return false;
}

bool myIsSymmetric(struct TreeNode *left,struct TreeNode *right) {
    if (left == NULL && right == NULL) {
        return true;
    } else if (left == NULL || right == NULL) {
        return false;
    }
    if (left->val != right->val) {
        return false;
    }
    if (myIsSymmetric(left->left, right->right) == false || myIsSymmetric(left->right, right->left) == false) {
        return false;
    }
    return true;//myIsSymmetric(left->left, right->right) && myIsSymmetric(left->right, right->left);
}

//对称二叉树
bool isSymmetric(struct TreeNode* root) {
    if (root==NULL) {
        return true;
    }
    return myIsSymmetric(root->left, root->right);
}

// 翻转二叉树 递归实现方式
struct TreeNode* invertTree(struct TreeNode* root) {
    if (!root) {
        return root;
    }
    if (!root->left && !root->right) {
        return root;
    }
    
    struct TreeNode *temp = root->left;
    root->left = root->right;
    root->right = temp;
    
    if (root->left) {
        invertTree(root->left);
    }
    
    if (root->right) {
        invertTree(root->right);
    }
    
    return root;
}