View Compilation Error

1_868_1394_6617.cpp: In function 'int main()':
1_868_1394_6617.cpp:23:19: error: the value of 'i' is not usable in a constant expression
             case(i):
                   ^
1_868_1394_6617.cpp:21:18: note: 'char i' is not const
         for(auto i:x)
                  ^
1_868_1394_6617.cpp:23:13: error: case label 'i' not within a switch statement
             case(i):
             ^
1_868_1394_6617.cpp:24:16: error: expected ';' before ':' token
             'a':cnt[0]++;break;
                ^
1_868_1394_6617.cpp:25:16: error: expected ';' before ':' token
             'v':cnt[1]++;break;
                ^
1_868_1394_6617.cpp:26:16: error: expected ';' before ':' token
             'i':cnt[2]++;break;
                ^
1_868_1394_6617.cpp:27:16: error: expected ';' before ':' token
             'n':cnt[3]++;break;
                ^