111. Minimum Depth of Binary Tree*
https://leetcode.com/problems/minimum-depth-of-binary-tree/
题目描述
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.
C++ 实现 1
主要考虑特殊情况, 比如说如果左子树不存在, 那么只需要求右子树的 minimum depth 再加 1 即可.
/**
* 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;
if (!root->left) return minDepth(root->right) + 1;
else if (!root->right) return minDepth(root->left) + 1;
else return std::min(minDepth(root->left), minDepth(root->right)) + 1;
}
};