leetcode dfs Minimum Depth of Binary Tree

Minimum Depth of Binary Tree

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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.

题意：求出二叉树的最小深度

思路：

minDepth(root) = 1 + min(minDepth(root->left), minDepth(root->right));

但如果 root -> left 或 root->right为空时，minDepth对他们的计算结果为返回 0 ,所以这两个要分别处理一下。

复杂度： 时间O(n) ，空间O(log n)

int minDepth(const TreeNode *root){
if(!root) return 0;
if(!root->left) return 1 + minDepth(root->right);
if(!root->right) return 1 + minDepth(root->left);
return 1 + min(minDepth(root->left), minDepth(root->right));
}