foo.cc: In function 'int main()':
foo.cc:24:21: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     f[0][(1<<(n+n)/2-1)]=1;
              ~~~~~~~^~
foo.cc:35:34: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
                     if (!(j&(1<<k-1))&&!(a[i]&(1<<k-1)))
                                 ~^~
foo.cc:35:52: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
                     if (!(j&(1<<k-1))&&!(a[i]&(1<<k-1)))
                                                   ~^~
foo.cc:36:33: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
                     f[x][j|(1<<k-1)]+=f[x^1][j];
                                ~^~

自豪的采用jd5进行评测(github.com/masnn/jd5)

{"receive":"2020-02-28T12:34:59.141Z","handle":"2020-02-28T12:34:59.141Z","cache_start":"2020-02-28T12:34:59.142Z","read_cases":"2020-02-28T12:35:01.715Z","judge":"2020-02-28T12:35:01.717Z","done":"2020-02-28T12:35:03.241Z"}