树
深度优先搜索
广度优先搜索
二叉搜索树
二叉树
题目描述
给你一个二叉搜索树的根节点 root
,返回 树中任意两不同节点值之间的最小差值 。
差值是一个正数,其数值等于两值之差的绝对值。
示例 1:
输入: root = [4,2,6,1,3]
输出: 1
示例 2:
输入: root = [1,0,48,null,null,12,49]
输出: 1
提示:
树中节点的数目范围是 [2, 100]
0 <= Node.val <= 105
注意: 本题与 530:https://leetcode.cn/problems/minimum-absolute-difference-in-bst/ 相同
解法
方法一:中序遍历
中序遍历二叉搜索树,获取当前节点与上个节点差值的最小值即可。
Python3 Java C++ Go JavaScript
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20 # Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution :
def minDiffInBST ( self , root : Optional [ TreeNode ]) -> int :
def dfs ( root ):
if root is None :
return
dfs ( root . left )
nonlocal ans , prev
ans = min ( ans , abs ( prev - root . val ))
prev = root . val
dfs ( root . right )
ans = prev = inf
dfs ( root )
return ans
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37 /**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
private int ans ;
private int prev ;
private int inf = Integer . MAX_VALUE ;
public int minDiffInBST ( TreeNode root ) {
ans = inf ;
prev = inf ;
dfs ( root );
return ans ;
}
private void dfs ( TreeNode root ) {
if ( root == null ) {
return ;
}
dfs ( root . left );
ans = Math . min ( ans , Math . abs ( root . val - prev ));
prev = root . val ;
dfs ( root . right );
}
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31 /**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public :
const int inf = INT_MAX ;
int ans ;
int prev ;
int minDiffInBST ( TreeNode * root ) {
ans = inf , prev = inf ;
dfs ( root );
return ans ;
}
void dfs ( TreeNode * root ) {
if ( ! root ) return ;
dfs ( root -> left );
ans = min ( ans , abs ( prev - root -> val ));
prev = root -> val ;
dfs ( root -> right );
}
};
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31 /**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func minDiffInBST ( root * TreeNode ) int {
inf := 0x3f3f3f3f
ans , prev := inf , inf
var dfs func ( * TreeNode )
dfs = func ( root * TreeNode ) {
if root == nil {
return
}
dfs ( root . Left )
ans = min ( ans , abs ( prev - root . Val ))
prev = root . Val
dfs ( root . Right )
}
dfs ( root )
return ans
}
func abs ( x int ) int {
if x < 0 {
return - x
}
return x
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 var minDiffInBST = function ( root ) {
let ans = Number . MAX_SAFE_INTEGER ,
prev = Number . MAX_SAFE_INTEGER ;
const dfs = root => {
if ( ! root ) {
return ;
}
dfs ( root . left );
ans = Math . min ( ans , Math . abs ( root . val - prev ));
prev = root . val ;
dfs ( root . right );
};
dfs ( root );
return ans ;
};