Daily Warmer Temperatures

July 10, 2025

Question

You’re given a list of daily temperatures. For each day, you need to find out how many days you'll have to wait until a warmer temperature. If there’s no warmer day ahead, just put 0 for that day.

This is like predicting the future weather — but only the wait time until it gets warmer.

Example

Input: [73, 74, 75, 71, 69, 72, 76, 73]

Output: [1, 1, 4, 2, 1, 1, 0, 0]

Explanation: For day 0 (temp 73), you’ll have to wait 1 day (temp 74). Day 2 (75) has to wait 4 days for a warmer day (76), and so on.

My Notes

Use a stack to keep track of indices of temperatures.
Loop backwards, starting from the last day.
Pop values from the stack that aren’t warmer than the current temperature.
The top of the stack (if exists) is the next warmer day.
Time complexity: O(n), since each index is pushed/popped once.

package main

import (
    "fmt"
)

type Stack struct {
    items []int
}

func (s *Stack) Push(item int) {
    s.items = append(s.items, item)
}

func (s *Stack) Pop() {
    s.items = s.items[:len(s.items)-1]
}

func (s *Stack) Top() int {
    return s.items[len(s.items)-1]
}

func (s *Stack) Empty() bool {
    return len(s.items) == 0
}

func dailyTemperatures(temperatures []int) []int {
    result := make([]int, len(temperatures))
    stack := Stack{}

    for i := len(temperatures) - 1; i >= 0; i-- {
        for !stack.Empty() && temperatures[stack.Top()] <= temperatures[i] {
            stack.Pop()
        }

        if !stack.Empty() {
            result[i] = stack.Top() - i
        }

        stack.Push(i)
    }

    return result
}

func main() {
    result := dailyTemperatures([]int{73, 74, 75, 71, 69, 72, 76, 73})
    fmt.Println(result)
}