View Compilation Error

0_0_38079010_17473.cpp: In function 'int main()':
0_0_38079010_17473.cpp:28:19: error: 'scanf' was not declared in this scope
     scanf("%d", &t);
                   ^
0_0_38079010_17473.cpp:37:26: error: 'sort' was not declared in this scope
         sort(a + 1, a + 5);    //排序
                          ^
0_0_38079010_17473.cpp:41:55: error: 'lower_bound' was not declared in this scope
             x[i] = 2 * (lower_bound(a + 1, a + 5, x[i]) - a);
                                                       ^
0_0_38079010_17473.cpp:44:33: error: 'memset' was not declared in this scope
         memset(mp, 0, sizeof(mp));
                                 ^
0_0_38079010_17473.cpp:62:9: error: 'cout' was not declared in this scope
         cout<<ans<<'\n';
         ^