【leetcode刷题笔记】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.

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题解：递归解决，用私有变量minDep保存最小的深度，每当遍历到叶节点的时候就看是否需要更新。

代码如下：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    private int minDep = Integer.MAX_VALUE;
    public void minDepthRecur(TreeNode root,int depth){
        if(root == null)
            return;
        if(root.left == null && root.right == null){
            if(minDep > depth)
                minDep = depth;
            return;
        }
        minDepthRecur(root.left, depth+1);
        minDepthRecur(root.right, depth+1);
    }
    public int minDepth(TreeNode root) {
        if(root == null)
            return 0;
        minDepthRecur(root, 1);
        return minDep;
    }
}