Daily Temperatures

temperatures[i] is the temperature on day i. Build an array answer where answer[i] counts the days from day i until the first strictly warmer day. If no warmer day ever comes, answer[i] stays 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.

Visualize how the monotonic stack keeps track of 'unresolved' cooler days.