The solution should be computed from right to left.

For the last element, the time needed to become zero is just the beginning height. Once we know the timing for the last element, we can go from right to left and calculate the total time each flower needs.

For any flower h[i], we know that it will take time h[i] after the time at which h[i+1] == h[i] — 1. In other words, a flower of height 7 will take 7 seconds after the next flower is at height 6. We know when h[i+1] is at height 6 by adding 6 to the time at which it is at 0. So, flower i will take h[i] + timing[i+1] — (h[i] — 1) which simplifies to timing[i+1] + 1. If there is a particularly larger h[i], its value may be more than timing[j+1]+1 so we just set timing[i] to h[i].