[LeetCode] 739. Daily Temperatures

 Problem : https://leetcode.com/problems/daily-temperatures/

Use monotonic stack to keep a decreasing sequence.

class Solution {
    fun dailyTemperatures(temperatures: IntArray): IntArray {
        val stack = Stack<int>()
        val result = IntArray(temperatures.size) { 0 }
        
        for (i in 0 until temperatures.size) {
            // pop all the days which temperature is lower than current day
            while (!stack.empty() && temperatures[stack.peek()] < temperatures[i]) {
                val last = stack.pop()
                result[last] = i - last 
            }
            
            stack.push(i)
        }
        
        return result
    }
}