530. Minimum Absolute Difference in BST

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可以对照563. Binary Tree Tilt

• 超时了，思路是把树种的值全部取出来放在list中，然后处理

class Solution(object):    def getMinimumDifference(self, root):        """        :type root: TreeNode        :rtype: int        """        self.l = []        def get(node):            if not node:                pass            else:                self.l.append(node.val)                get(node.left)                get(node.right)        get(root)        print self.l        min_c = 10000        for i in range(len(self.l)):            for j in range(len(self.l)):                if i != j:                    if abs(self.l[i]-self.l[j]) < min_c:                        min_c = abs(self.l[i]-self.l[j])        return min_c

• 不是很懂什么叫做BST，可以参考这篇文章BST树，原来这个树是已经排好序的；这样比较起来会快很多

class Solution(object):    def getMinimumDifference(self, root):        """        :type root: TreeNode        :rtype: int        """        def get(node):            return get(node.left)+[node.val]+get(node.right) if node else []        min_c = 1000000        l = get(root)        for i in range(len(l)-1):            if min_c > abs(l[i]-l[i+1]):                min_c = abs(l[i]-l[i+1])        return min_c

 for i in range(len(l)-1):            if min_c > abs(l[i]-l[i+1]):                min_c = abs(l[i]-l[i+1])        return min_c

可以替换成

return min(abs(l[i]-l[i+1]) for i in range(len(l)-1))

这种精简的写法值得学习