Second Minimum Node In a Binary Tree

给一个很特殊的二叉树, 返回第二小的值. 直接都放到list里, 然后找到值

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int findSecondMinimumValue(TreeNode root) {
        List<Integer> list = new ArrayList<>();
        bfs(root, list);
        Collections.sort(list);
        int first = -1;
        int second = -1;
        for(Integer i : list) {
            if(first == -1){
                first = i;
            } else if(i != first) {
                second = i;
                break;
            }
        }
        return second;
    }
    
    private void bfs(TreeNode root, List<Integer> list) {
        if(root == null)
            return;
        list.add(root.val);
        bfs(root.left, list);
        bfs(root.right, list);
    }
}

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

class Solution {

public int findSecondMinimumValue(TreeNode root) {

List<Integer> list = new ArrayList<>();

bfs(root, list);

Collections.sort(list);

int first = -1;

int second = -1;

for(Integer i : list) {

if(first == -1){

first = i;

} else if(i != first) {

second = i;

break;

}

return second;

}

private void bfs(TreeNode root, List<Integer> list) {

if(root == null)

return;

list.add(root.val);

bfs(root.left, list);

bfs(root.right, list);

}

Second Minimum Node In a Binary Tree

书脊

这青苔碧瓦堆, 俺曾睡风流觉, 将五十年兴亡看饱.

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