foo.cc: In function 'void tree_dp(long long int, long long int)':
foo.cc:51:26: warning: iteration 3 invokes undefined behavior [-Waggressive-loop-optimizations]
             ans+=dp[to][j]*dp[from][((-j-val)%7+7)%7]*6;
                  ~~~~~~~~^
foo.cc:11:42: note: within this loop
 #define rep(i,s,e) for(register int i=s;i<=e;++i)
foo.cc:50:13:
         rep(j,0,6)
             ~~~~~                         
foo.cc:50:9: note: in expansion of macro 'rep'
         rep(j,0,6)
         ^~~
foo.cc:53:42: warning: iteration 3 invokes undefined behavior [-Waggressive-loop-optimizations]
             dp[from][(j+val)%7]+=dp[to][j];
                                  ~~~~~~~~^
foo.cc:11:42: note: within this loop
 #define rep(i,s,e) for(register int i=s;i<=e;++i)
foo.cc:52:13:
         rep(j,0,6)
             ~~~~~                         
foo.cc:52:9: note: in expansion of macro 'rep'
         rep(j,0,6)
         ^~~

自豪的采用 HydroJudge 进行评测(github.com/hydro-dev/HydroJudge)

{"receive":"2020-08-07T05:40:23.003Z","handle":"2020-08-07T05:40:23.003Z","cache_start":"2020-08-07T05:40:23.009Z","read_cases":"2020-08-07T05:40:23.136Z","judge":"2020-08-07T05:40:23.136Z","done":"2020-08-07T05:40:24.023Z"}