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.

 

class Solution {

    public int minDepth(TreeNode root) {

        if (root == null) return 0;

        int left = minDepth(root.left);

        int right = minDepth(root.right);

        return (left == 0 || right == 0) ? left + right + 1 : Math.min(left, right) + 1; //在叶节点的父节点也许会出现(left == 0 || right == 0)

    }

}