foo.cc: In function 'void prepare()':
foo.cc:17:16: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (!vis[x[i]]) {
                ^
foo.cc:19:12: warning: array subscript has type 'char' [-Wchar-subscripts]
    vis[x[i]] = 1;
            ^
foo.cc:21:16: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (!vis[y[i]]) {
                ^
foo.cc:23:12: warning: array subscript has type 'char' [-Wchar-subscripts]
    vis[y[i]] = 1;
            ^
foo.cc:25:16: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (!vis[z[i]]) {
                ^
foo.cc:27:12: warning: array subscript has type 'char' [-Wchar-subscripts]
    vis[z[i]] = 1;
            ^
foo.cc: In function 'bool check()':
foo.cc:34:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (a[x[i]] == -1 || a[y[i]] == -1 || a[z[i]] == -1)
             ^
foo.cc:34:30: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (a[x[i]] == -1 || a[y[i]] == -1 || a[z[i]] == -1)
                              ^
foo.cc:34:47: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (a[x[i]] == -1 || a[y[i]] == -1 || a[z[i]] == -1)
                                               ^
foo.cc:38:16: warning: array subscript has type 'char' [-Wchar-subscripts]
     if ((a[x[i]] + a[y[i]]) % n == a[z[i]])
                ^
foo.cc:38:26: warning: array subscript has type 'char' [-Wchar-subscripts]
     if ((a[x[i]] + a[y[i]]) % n == a[z[i]])
                          ^
foo.cc:38:42: warning: array subscript has type 'char' [-Wchar-subscripts]
     if ((a[x[i]] + a[y[i]]) % n == a[z[i]])
                                          ^
foo.cc:39:18: warning: array subscript has type 'char' [-Wchar-subscripts]
      jw = (a[x[i]] + a[y[i]]) / n;
                  ^
foo.cc:39:28: warning: array subscript has type 'char' [-Wchar-subscripts]
      jw = (a[x[i]] + a[y[i]]) / n;
                            ^
foo.cc:40:21: warning: array subscript has type 'char' [-Wchar-subscripts]
     else if ((a[x[i]] + a[y[i]] + 1) % n == a[z[i]])
                     ^
foo.cc:40:31: warning: array subscript has type 'char' [-Wchar-subscripts]
     else if ((a[x[i]] + a[y[i]] + 1) % n == a[z[i]])
                               ^
foo.cc:40:51: warning: array subscript has type 'char' [-Wchar-subscripts]
     else if ((a[x[i]] + a[y[i]] + 1) % n == a[z[i]])
                                                   ^
foo.cc:41:18: warning: array subscript has type 'char' [-Wchar-subscripts]
      jw = (a[x[i]] + a[y[i]] + 1) / n;
                  ^
foo.cc:41:28: warning: array subscript has type 'char' [-Wchar-subscripts]
      jw = (a[x[i]] + a[y[i]] + 1) / n;
                            ^
foo.cc:45:20: warning: array subscript has type 'char' [-Wchar-subscripts]
    else if ((a[x[i]] + a[y[i]] + jw) % n == a[z[i]])
                    ^
foo.cc:45:30: warning: array subscript has type 'char' [-Wchar-subscripts]
    else if ((a[x[i]] + a[y[i]] + jw) % n == a[z[i]])
                              ^
foo.cc:45:51: warning: array subscript has type 'char' [-Wchar-subscripts]
    else if ((a[x[i]] + a[y[i]] + jw) % n == a[z[i]])
                                                   ^
foo.cc:46:17: warning: array subscript has type 'char' [-Wchar-subscripts]
     jw = (a[x[i]] + a[y[i]] + jw) / n;
                 ^
foo.cc:46:27: warning: array subscript has type 'char' [-Wchar-subscripts]
     jw = (a[x[i]] + a[y[i]] + jw) / n;
                           ^

自豪的采用jd5进行评测(github.com/masnn/jd5)