foo.cpp: In function 'int main()':
foo.cpp:14:19: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
    if (c[n] = b[0])
                   ^
foo.cpp:18:13: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  std::cout<<sum<<std::endl;
             ^~~