View Compilation Error

0_0_39452937_16641.cpp:2:5: error: 'a' does not name a type
    2 |     a->sum += b->sum;
      |     ^
0_0_39452937_16641.cpp:3:5: error: 'a' does not name a type
    3 |     a->cnt += b->cnt;
      |     ^
0_0_39452937_16641.cpp:4:14: error: 'l' was not declared in this scope
    4 |     int m = (l + r) / 2;
      |              ^
0_0_39452937_16641.cpp:4:18: error: 'r' was not declared in this scope
    4 |     int m = (l + r) / 2;
      |                  ^
0_0_39452937_16641.cpp:5:5: error: expected unqualified-id before 'if'
    5 |     if (a->l != nullptr && b->r != nullptr) {
      |     ^~
0_0_39452937_16641.cpp:8:5: error: expected unqualified-id before 'if'
    8 |     if (b->l != nullptr && a->r != nullptr) {
      |     ^~