foo.cc: In function 'int main()':
foo.cc:8:53: warning: unused variable 'c' [-Wunused-variable]
    8 |         int a1[100000] = { 0 }, a2[100000] = { 0 }, c[100000] = { 0 };//有啥作用;
      |                                                     ^
foo.cc:12:13: warning: unused variable 'i' [-Wunused-variable]
   12 |         int i;
      |             ^

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