739. Daily Temperatures

Medium

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

解題

O(n)

可以參考這個影片的講解。

func dailyTemperatures(temperatures []int) []int {
    stack := make([]int, 0)
    res := make([]int, len(temperatures))

    for i, t := range temperatures {
        for len(stack) != 0 {
            top := stack[len(stack) - 1]
            if temperatures[top] < t {
                res[top] = i - top
                stack = stack[:len(stack) - 1]
            } else {
                break
            }
        }

        stack = append(stack, i) 
    }

    return res
}