To find the number of character array reverse order (poj1007)

int Inversionnumber (char* s,int len)

• {
• int ans=0; //s Reverse order number
• int a,c,g; //each letter occurrence, T is the largest, no need to calculate the number of T occurrences
• a=c=g=0;
• For (int i=len-1;i>=0;i--)
• {
• switch (s[i])
• {
• case ' A ': a++;   Break //a is the smallest, no reverse number
• case ' C ':
• {
• C + +;
• Ans+=a; //The number of times A is present after C is the inverse of this C
• Break ;
• }
• case ' G ':
• {
• g++;
• Ans+=a;
• Ans+=c;
• Break ;
• }
• case ' T ':
• {
• Ans+=a;
• Ans+=c;
• ans+=g;
• Break ;
• }
• }
• }
• return ans;
• }

To find the number of character array reverse order (poj1007)