Minimum Depth of Binary Tree

    题解

    2.  * Definition of TreeNode:
    3.  * public class TreeNode {
    4.  *     public int val;
    5.  *     public TreeNode left, right;
    6.  *         this.val = val;
    7.  *         this.left = this.right = null;
    8.  *     }
    9.  * }
    11. public class Solution {
    12.     /**
    13.      * @param root: The root of binary tree.
    14.      * @return: An integer.
    15.      */
    16.     public int minDepth(TreeNode root) {
    17.         if (root == null) return 0;
    18.         int leftDepth = minDepth(root.left);
    21.         // current node is not leaf node
    22.         if (root.left == null) {
    23.             return 1 + rightDepth;
    24.         } else if (root.right == null) {
    25.             return 1 + leftDepth;
    26.         }
    28.         return 1 + Math.min(leftDepth, rightDepth);