L155 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.

这题跟前面一体Max deapth很像，不过要注意只有一个node的情况。

public int minDepth(TreeNode root) {
    if (root == null) {
        return 0;
    }

    int left = minDepth(root.left);
    int right = minDepth(root.right);

    if (left > 0 && right > 0) {
        return Math.min(left, right) + 1;
    } else if (left > 0) {
        return left + 1;
    } else if (right > 0) {
        return right + 1;
    } else {
        return 1;
    }
}