Title
Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7],
3
/ \
9 20
/ \
15 7
return its minimum depth = 2.
求树最小的深度，要注意陷阱，如果仅有一个孩子的话，就不是min(left,right)+1了，因为有个0，所以是其中一个+1
Solution
//cpp:
/**
* 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 minDepth(TreeNode* root) {
if(!root)
return 0;
int l=minDepth(root->left);
int r=minDepth(root->right);
return (l==0||r==0)?l+r+1:min(l,r)+1;
}
};