View Compilation Error

0_0_39541676_26248.cpp:1:8: error: 'a' was not declared in this scope
    1 | int t1=a[i].id,t2=a[i-1].id;
      |        ^
0_0_39541676_26248.cpp:1:10: error: 'i' was not declared in this scope
    1 | int t1=a[i].id,t2=a[i-1].id;
      |          ^
0_0_39541676_26248.cpp:3:9: error: 'G' does not name a type
    3 |         G[t1].push_back({t2,w});
      |         ^
0_0_39541676_26248.cpp:3:31: error: expected unqualified-id before ')' token
    3 |         G[t1].push_back({t2,w});
      |                               ^
0_0_39541676_26248.cpp:4:9: error: 'G' does not name a type
    4 |         G[t2].push_back({t1,w});
      |         ^
0_0_39541676_26248.cpp:4:31: error: expected unqualified-id before ')' token
    4 |         G[t2].push_back({t1,w});
      |                               ^