Daily Temperatures

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 i-th day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0.

We use a Monotonic Decreasing Stack.

1. Initialize answer array with 0s.
2. Use a stack to store indices of days.
3. Iterate through temperatures.
4. While the current temperature is warmer than the temperature at the index stored in stack.top():
   • We found a warmer day for stack.top()!
   • Pop the index (prevIndex).
   • Calculate days waiting: i - prevIndex.
   • Update answer[prevIndex].
5. Push current index i onto the stack.