LeetCode -- Minimum Depth of Binary Tree

LeetCode -- Minimum Depth of Binary Tree

題目描述：


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.


就是求一個樹的最小層數。


思路：
從根節點進行BFS ，找到第一個葉子節點即可。


實現代碼：

/**
 * 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;
        }
        
        var layer = 1;
        var nodes = new List();
        LoadChildren(ref nodes, root);
        if(nodes.Count == 0){
            return layer;
        }
        
        layer ++;
        
        MinDepth(nodes,ref layer);
        return layer;
    }
    private void MinDepth(List parents, ref int layer){
        var next = new List();
        for(var i = 0;i < parents.Count; i++){
            if(parents[i].left == null && parents[i].right == null){
                return;
            }
            if(parents[i].left != null){
                next.Add(parents[i].left);
            }
            if(parents[i].right != null){
                next.Add(parents[i].right);
            }
        }
        
        layer ++;
        MinDepth(next,ref layer);
    }
    private void LoadChildren(ref List nodes, TreeNode node){
        if(node.left != null){
            nodes.Add(node.left);
        }
        if(node.right != null){
            nodes.Add(node.right);
        }
    }
}