In this post, we are going to solve the 111. Minimum Depth of Binary Tree problem of Leetcode. This problem 111. Minimum Depth of Binary Tree is a Leetcode easy level problem. Let’s see the code, 111. Minimum Depth of Binary Tree – Leetcode Solution.

Problem

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 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

Constraints

• The number of nodes in the tree is in the range [0, 105].
• -1000 <= Node.val <= 1000

Now, let’s see the code of 111. Minimum Depth of Binary Tree – Leetcode Solution.

Minimum Depth of Binary Tree – Leetcode Solution

111. Minimum Depth of Binary Tree – Solution in Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int minDepth(TreeNode root) {
        if(root == null) return 0;
        int left = minDepth(root.left);
        int right = minDepth(root.right);
        
        return (left == 0 || right == 0) ? left + right + 1 : Math.min(left,right)+1;
    }
}

111. Minimum Depth of Binary Tree – Solution in C++

/**
 * 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 minDepth(TreeNode* root) {
        if (!root) return 0;
        int L = minDepth(root->left), R = minDepth(root->right);
        return 1 + (min(L, R) ? min(L, R) : max(L, R));
    }
};

111. Minimum Depth of Binary Tree – Solution in Python

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def minDepth(self, root):
        if not root: return 0
        d = map(self.minDepth, (root.left, root.right))
        return 1 + (min(d) or max(d))
        

Note: This problem 111. Minimum Depth of Binary Tree is generated by Leetcode but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.