foo.cc: In function 'bool spfa(int)':
foo.cc:30:61: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   30 |     for (int i = 1; i <= n; ++i) d[i] = inf, inq[i] = nc[i] = 0;
      |                                                       ~~~~~~^~~
foo.cc:32:20: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   32 |     inq[s] = nc[s] = 1;
      |              ~~~~~~^~~

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