感觉measure还是些麻烦了吧，我这么写的：
...
int measure=0
int A,C,G,T;
A=C=G=T=0;
for(char* p=str;*p;p++){
    switch(*p){
    case 'A':
        measure+=C+G+T;
        ++A;
        break;
     case 'C':
        measure+=G+T;
        ++C;
        break;
     case 'G':
        measure+=T;
        ++G;
        break;
     case 'T':
         ++T;
         break;
     }
}