# Minimum Depth of Binary Tree

111. Minimum Depth of Binary Tree

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.

``````/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int minDepth(TreeNode root) {
if (root == null) {
return 0;
}

if (root.left == null && root.right == null) {
return 1;
}

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

int depth = 0;

queue.offer(root);

while (!queue.isEmpty()) {
depth++;

int size = queue.size();

for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();

if (node.left == null && node.right == null) {
return depth;
}

if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
}

return depth;
}
}
``````

Hope this helps,
Michael