平衡二叉树

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     struct TreeNode *left;*     struct TreeNode *right;* };*/int MAX(int a,int b)
{return a > b ? a : b;
}//求高度
int getHeight(struct TreeNode *root){if(root == NULL){return 0;}int left =getHeight(root->left);int right =getHeight(root->right);return MAX(left,right)+1;
}
bool isBalanced(struct TreeNode* root){if(root == NULL){return true;}//左子树是不是平衡二叉树bool is_left_balance =isBalanced(root->left);if(is_left_balance == false){return false;}//右子树是不是平衡二叉树bool is_right_balance =isBalanced(root->right);if(is_right_balance == false){return false;}int left_height = getHeight(root->left);int right_height = getHeight(root->right);int diff =left_height-right_height;//左右子树高度差要小于1	if(diff >= -1 && diff <=1){return true;}else{return false;}
}

根据二叉树创建字符串

class Solution {
public:string tree2str(TreeNode* t) {if(t==nullptr)return "";stringstream ss;function<void(TreeNode*)> helper = [&ss, &helper](TreeNode* t){ss<<t->val;if(t->left==nullptr){if(t->right!=nullptr){ss<<"()(";helper(t->right);ss<<')';}}else if(t->right==nullptr){ss<<'(';helper(t->left);ss<<')';}else{ss<<'(';helper(t->left);ss<<")(";helper(t->right);ss<<')';}};helper(t);string s;ss>>s;return s;}
};