https://leetcode.com/problems/minimum-depth-of-binary-tree/description/
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.
题解:注意左右子树是否非空
class Solution {
public:
int minDepth(TreeNode* root) {
if (root == NULL){
return 0;
}
while (root != NULL){
if (root->left == NULL && root->right != NULL){
return minDepth(root->right) + 1;
}
if (root->left != NULL && root->right == NULL){
return minDepth(root->left) + 1;
}
return min(minDepth(root->left), minDepth(root->right)) + 1;
}
}
};