111.minimum-depth-of-binary-tree.131493401.ac.java

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