p111

 

 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class  {
    public int ans = Integer.MAX_VALUE;

	public int minDepth(TreeNode root) {
		if (root == null)
			return 0;
		if (root.left == null && root.right == null) {

			return 1;
		}
		
		minDepth(root,0);
		return ans;
	}

	public void minDepth(TreeNode root, int d) {

		if (d >= ans)
			return;
		if (root.left == null && root.right == null) {
			ans = Math.min(d + 1, ans);
		}
		if (root.left != null) {
			minDepth(root.left, d + 1);
		}

		if (root.right != null) {
			minDepth(root.right, d + 1);
		}

		return;
	}
}