LeetCode104.二叉树的最大深度

题目

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root == NULL) return 0;
        //return maxDepth(root->left) > maxDepth(root->right) ? maxDepth(root->left)+1:maxDepth(root->right)+1;
        return max(maxDepth(root->left) , maxDepth(root->right)) +1;
    }
};

第5行还不清楚为什么会超时？条件运算符要慢？

法二、用层次遍历的思想也要会

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root == NULL) return 0;
        queue<TreeNode*> q;
        q.push(root);
        int depth = 0;
        while(!q.empty()) {
            int num = q.size();
            while(num > 0){
                TreeNode *p = q.front();q.pop();
                if(p->left != NULL) q.push(p->left);
                if(p->right != NULL) q.push(p->right);
                num--;
            }
            depth++;
        }
        return depth;
    }
};