foo.cc: In function 'bool construct(int, int*, int)':
foo.cc:25:1: warning: no return statement in function returning non-void [-Wreturn-type]
   25 | }
      | ^
foo.cc: In function 'int main()':
foo.cc:46:9: error: 'qsort' was not declared in this scope
   46 |         qsort(a, cnt, sizeof(int), cmp);
      |         ^~~~~

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