111. Minimum Depth of Binary Tree
Given a binary tree, find its minimum depth.
Minimum depth is the number of nodes on the shortest path from the root node to the next leaf node.
Note: A leaf is a node that has no children.
Example 1:
Input: Root = [3,9,20,null,null,15,7]
Output: 2
Example 2:
Input: Root = [2,null,3, null,4,null,5,null,6]
Output: 5
Limits:
The range of nodes in the tree is [0, 105].
-1000 <= Node.val <= 1000
Solution
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
int solve(TreeNode *root){
if(root==NULL){
return 0;
}
if(root->left == NULL && root->right ==NULL){
return 1;
}
int l = solve(root->left);
int r = solve(root->right);
if(l!=0 && r!=0){
return 1+min(l,r);
}
else if(l==0){
return 1+r;
}
else if(r==0){
return 1+l;
}
// return 1+min(l,r);
return -1;
}
int minDepth(TreeNode* root) {
return solve(root);
}
};
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