View Compilation Error

0_0_22704193_14038.cpp: In function 'void dfs1(int, int, int)':
0_0_22704193_14038.cpp:62:2: error: 'b' was not declared in this scope
  b[idx] = c[u];
  ^
0_0_22704193_14038.cpp: In function 'void build(int, int, int)':
0_0_22704193_14038.cpp:87:15: error: 'b' was not declared in this scope
   tree[id].pb(b[l]);
               ^