Every node in the tree has the property that the line that maximizes its midpoint is found either in the node or one of its ancestors. When we visit a node, we compute the winner at the midpoint of the node. The winner is stored in the node. The loser can still possibly beat the winner on some segment, either to the left or to the right of the current midpoint, so we propagate it to that segment.
(&mut self, mut m: i64, mut b: i64, l: i64, r: i64)
source not stored for this graph (policy: none)