739. Daily Temperatures

题目

Given a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.

For example, given the list of temperatures T = [73, 74, 75, 71, 69, 72, 76, 73], your output should be [1, 1, 4, 2, 1, 1, 0, 0].

Note: The length of temperatures will be in the range [1, 30000]. Each temperature will be an integer in the range [30, 100].

题目大意

给出一个温度数组，要求输出比当天温度高的在未来的哪一天，输出未来第几天的天数。例如比 73 度高的在未来第 1 天出现，比 75 度高的在未来第 4 天出现。

解题思路

这道题根据题意正常处理就可以了。2 层循环。另外一种做法是单调栈，维护一个单调递减的单调栈即可。

代码

package leetcode

// 解法一 普通做法
func dailyTemperatures(T []int) []int {
	res, j := make([]int, len(T)), 0
	for i := 0; i < len(T); i++ {
		for j = i + 1; j < len(T); j++ {
			if T[j] > T[i] {
				res[i] = j - i
				break
			}
		}
	}
	return res
}

// 解法二 单调栈
func dailyTemperatures1(T []int) []int {
	res := make([]int, len(T))
	var toCheck []int
	for i, t := range T {
		for len(toCheck) > 0 && T[toCheck[len(toCheck)-1]] < t {
			idx := toCheck[len(toCheck)-1]
			res[idx] = i - idx
			toCheck = toCheck[:len(toCheck)-1]
		}
		toCheck = append(toCheck, i)
	}
	return res
}

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