##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######
##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######
The pattern
Two passes: left-to-right, then right-to-left.
Left-to-right: if rating[i] > rating[i-1], give candy[i] = candy[i-1] + 1.
Right-to-left: if rating[i] > rating[i+1], candy[i] must be at least candy[i+1] + 1.
Take the max of both passes for each child. This satisfies both neighbor constraints.
