foo.c:2:1: error: unknown type name ‘using’
    2 | using namespace std;
      | ^~~~~
foo.c:2:17: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘std’
    2 | using namespace std;
      |                 ^~~
foo.c:5:5: error: unknown type name ‘string’
    5 |     string name;//名字
      |     ^~~~~~
foo.c:12:1: error: unknown type name ‘bool’
   12 | bool cmp(obj a, obj b){//比较函数
      | ^~~~
foo.c:1:1: note: ‘bool’ is defined in header ‘<stdbool.h>’; did you forget to ‘#include <stdbool.h>’?
  +++ |+#include <stdbool.h>
    1 | 
foo.c:12:10: error: unknown type name ‘obj’
   12 | bool cmp(obj a, obj b){//比较函数
      |          ^~~
foo.c:12:17: error: unknown type name ‘obj’
   12 | bool cmp(obj a, obj b){//比较函数
      |                 ^~~
foo.c: In function ‘main’:
foo.c:21:5: error: ‘cin’ undeclared (first use in this function)
   21 |     cin>>n;
      |     ^~~
foo.c:21:5: note: each undeclared identifier is reported only once for each function it appears in
foo.c:35:5: warning: implicit declaration of function ‘sort’ [-Wimplicit-function-declaration]
   35 |     sort(arr+1,arr+1+n,cmp);
      |     ^~~~
foo.c:35:24: error: ‘cmp’ undeclared (first use in this function)
   35 |     sort(arr+1,arr+1+n,cmp);
      |                        ^~~
foo.c:36:5: error: ‘cout’ undeclared (first use in this function)
   36 |     cout<<arr[1].name<<endl;//奖金最多的人的名字
      |     ^~~~
foo.c:36:24: error: ‘endl’ undeclared (first use in this function)
   36 |     cout<<arr[1].name<<endl;//奖金最多的人的名字
      |                        ^~~~