動機

現在只要用到stack就會讓我想到merge interval

Problem

Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait after the ith day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0 instead.

 

Example 1:

Input: temperatures = [73,74,75,71,69,72,76,73]Output: [1,1,4,2,1,1,0,0]

Example 2:

Input: temperatures = [30,40,50,60]Output: [1,1,1,0]

Example 3:

Input: temperatures = [30,60,90]Output: [1,1,0]

 

Constraints:

  • 1 <= temperatures.length <= 105
  • 30 <= temperatures[i] <= 100

Sol

stack的promise是底下的大於上面的

class Solution:
    def dailyTemperatures(self, T: List[int]) -> List[int]:
        stk = [len(T)-1] # promise: stk[i] > stk[j]
        ret = [0]
        for i in reversed(range(len(T)-1)):
            while stk and T[stk[-1]] <= T[i]:
                stk.pop()
            if not stk:
                ret.append(0)
            else:
                ret.append(stk[-1]-i)
            stk.append(i)
        ret.reverse()
        return ret