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

Q: seeking a minimum depth of a given binary tree. The minimum depth of the root of the tree is the number of the shortest path to the nearest node of the leaf node.
A binary Tree GIVEN, depth.The Find ITS Minimum Minimum Number of Nodes The depth IS Along The Shortest The path from the root to Down The Nearest Leaf Node Node.
A:
Note that, it must be the root node to the leaf node. So to judge whether or not the root node with children.

    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;
    }