Main.cc: In function ‘int main()’: Main.cc:19:2: error: reference to ‘rank’ is ambiguous rank(a, 5);//成绩从高往低的一个排序 ^~~~ Main.cc:4:6: note: candidates are: void rank(int*, int) void rank(int b[], int len) { ^~~~ In file included from /usr/include/c++/7/bits/move.h:54:0, from /usr/include/c++/7/bits/nested_exception.h:40, from /usr/include/c++/7/exception:143, from /usr/include/c++/7/ios:39, from /usr/include/c++/7/ostream:38, from /usr/include/c++/7/iostream:39, from Main.cc:1: /usr/include/c++/7/type_traits:1468:12: note: template struct std::rank struct rank ^~~~