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.

Solution

/**
 * 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;

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

        int left = minDepth(root.left);
        int right = minDepth(root.right);

        if (left == 0) {
            return 1 + right; 
        } else if (right == 0) {
            return 1 +left;
        } else {
            return 1 + Math.min(left, right);
        }
    }
}