题目
The next greater element of some element x in an array is the first greater element that is to the right of x in the same array.
You are given two distinct 0-indexed integer arrays nums1 and nums2, where nums1 is a subset of nums2.
For each 0 <= i < nums1.length, find the index j such that nums1[i] == nums2[j] and determine the next greater element of nums2[j] in nums2. If there is no next greater element, then the answer for this query is -1.
Return an array ans of length nums1.length such that ans[i] is the next greater element as described above.
解题思路
使用单调栈处理nums2，找到每个元素后面最大的数是什么，将结果存在字典中，再通过nums1，生成结果
代码
class Solution:
def nextGreaterElement(self, nums1: List[int], nums2: List[int]) -> List[int]:
res = {}
s = []
for n in nums2[::-1]:
while s and n >= s[-1]:
s.pop()
res[n] = s[-1] if s else -1
s.append(n)
return [res[n] for n in nums1]
