Monotonic Stack — Daily Temperatures

Given an array temps of daily temperatures, return an array answer where
answer[i] is the number of days you have to wait after day i to get a
warmer temperature. If there is no warmer day, answer[i] is 0.

The brute force (scan forward from every day) is O(n²). Get it to O(n) with a
stack of indices whose temperatures are still waiting for a warmer day.

Examples

solve([73, 74, 75, 71, 69, 72, 76, 73])  → [1, 1, 4, 2, 1, 1, 0, 0]
solve([30, 40, 50, 60])                  → [1, 1, 1, 0]
solve([30, 60, 90])                      → [1, 1, 0]

Constraints

• 1 <= temps.length <= 100000
• "Warmer" means strictly greater — an equal temperature does not count.