Method update

code/data-structures/segment_tree_node.cpp:10–10

  node(int _l, int _r, ll _x) : node(_l,_r) { x = _x; }
  node(node a, node b) : node(a.l,b.r) { x = a.x + b.x; }
  void update(ll v) { x = v; }
  void range_update(ll v) { lazy = v; }
  void apply() { x += lazy * (r - l + 1); lazy = 0; }
  void push(node &u) { u.lazy += lazy; } };