Leetcode——minimum-depth-of-binary-tree

Q：求给定二叉树的最小深度。最小深度是指树的根结点到最近叶子结点的最短路径上结点的数量。
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.
A：
注意，一定要是根节点到叶节点的。所以要判断根节点是否有孩子。

    public int run(TreeNode root) {
        if (root == null)
            return 0;
        int l = run(root.left);
        int r = run(root.right);
        return (min(l, r)) + 1;
    }

    public int min(int a, int b) {
        if (a == 0)
            return b;
        if (b == 0)
            return a;
        return a < b ? a : b;
    }