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.

 

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int MinDepth(TreeNode root) {
        if (root == null) return 0;
        
        if (root.left != null && root.right != null)
        {
            return Math.Min(MinDepth(root.left), MinDepth(root.right)) + 1;
        }
        else if (root.left != null)
        {
            return MinDepth(root.left) + 1;
        }
        else
        {
            return MinDepth(root.right) + 1;
        }
    }
}

public class Solution1 {
    public int MinDepth(TreeNode root) {
        if (root == null) return 0;
        
        var minDepth = new int[1] {Int32.MaxValue};
        DFS(root, 1, minDepth);
        return minDepth[0];
    }
    
    private void DFS(TreeNode node, int cur, int[] minDepth)
    {
        if (node.left == null && node.right == null)
        {
            minDepth[0] = Math.Min(cur, minDepth[0]);
            return;
        }
        
        if (node.left != null) DFS(node.left, cur + 1, minDepth);
        if (node.right != null) DFS(node.right, cur + 1, minDepth);
    }
}