Leetcode上写二叉树求最大深度的代码
创建的栈没有初始压入元素,以为空栈调用top函数会返回NULL。
然后调试了好久发现top可能有古怪。
百度了一下发现top返回的是超尾-1,所以
The top function returns the topmost element of the stack. You should ensure that there are one or more elements on the stack before calling the top function.
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int maxDepth(TreeNode* root) {
TreeNode* f=root;
int d=1,max=0,c;
stack<TreeNode*> p;
stack<int> s;
p.push(NULL);
s.push(0);
while(f||p.size()>1)
{
if(f->left&&f->right&&f!=p.top())
{
TreeNode* t=f;
p.push(t);
f=f->left;
d++;
c=d;
s.push(c);
continue;
}
if(f->left&&f->right&&f==p.top())
{
p.pop();
f=f->right;
s.pop();
continue;
}
if(f->left)
{f=f->left;d++;continue;}
if(f->right)
{f=f->right;d++;continue;}
if(!f->left&&!f->right)
{
if(max<d)
max=d;
f=p.top();
d=s.top(); }
}
return max;
}
};