View Compilation Error

0_0_26406651_24521.cpp: In function 'int main()':
0_0_26406651_24521.cpp:133:24: error: 'class std::vector<int>' has no member named 'pb'
                 ans[k].pb(a), ans[k].pb(b);
                        ^
0_0_26406651_24521.cpp:133:38: error: 'class std::vector<int>' has no member named 'pb'
                 ans[k].pb(a), ans[k].pb(b);
                                      ^
0_0_26406651_24521.cpp:140:26: error: 'class std::vector<int>' has no member named 'pb'
             ans[cake[i]].pb(i);
                          ^