LeetCode 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.

public int minDepth(TreeNode root) {
if (root == null) return 0;
int rightDepth = minDepth(root.right);
int leftDepth = minDepth(root.left);
if (rightDepth != 0 && leftDepth != 0)
return Math.min(leftDepth, rightDepth) + 1;
return rightDepth != 0 ? rightDepth + 1 : leftDepth + 1;
}