Topcoder SRM 597 DIV 1

250 LittleElephantAndString

class LittleElephantAndString {private:        int ch[300];public:int getNumber(string A, string B) {        int ans=0;        int n=A.length();        int p=n;        memset(ch,0,sizeof(ch));        for (int i=0;i<n;i++){            ch[(int)A[i]]++;        }        for (int i=0;i<n;i++){            ch[(int)B[i]]--;        }        for (int i=0;i<300;i++){            if (ch[i]!=0) return -1;        }        for (int i=n-1;i>=0;i--){            bool ok=false;            for (int j=p-1;j>=0;j--){                if (A[j]==B[i]){                    ans++;                    p=j;                    ok=true;                    break;                }            }            if (!ok) break;        }        return n-ans;}};