Convex hull
1. in the cmp ar [1] written ar [2]: the ar [1] define root to be resolved (2020.3.11 Night)
2. tot mistake and to n: n only a local variable, the convex hull point to maintain a tot (2020.3.11 night)
1. in the cmp ar [1] written ar [2]: the ar [1] define root to be resolved (2020.3.11 Night)
2. tot mistake and to n: n only a local variable, the convex hull point to maintain a tot (2020.3.11 night)