LeetCode 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.

Note: A leaf is a node with no children.

 public int minDepth(TreeNode root) {
        /**
         * 求树的最小深度
         * 采用分治法
         * 1.将大问题分成子问题，分别进行求解
         * 2.将子问题合并成大问题的解
         */
        if (root == null) {
            return 0;
        }

        //divide步，分别求解子树的最小深度
        int right = minDepth(root.right);
        int left = maxDepth(root.left);
        
        //merge步，根据子树的最小深度，求解
        if (right == 0 || left == 0) {
            return right == 0 ? left : right;
        }
        return Math.min(minDepth(root.right), minDepth(root.left)) + 1;
    }