DNA Sorting Time Limit:1000MS  Memory Limit:10000K Description One measure of ``unsortedness'' in a sequence is the number of pairs of entries that are out of order with respect to each other. For instance, in the letter sequence ``DAABEC'', this measure is 5, since D is greater than four letters to its right and E is greater than one letter to its right. This measure is called the number of inversions in the sequence. The sequence ``AACEDGG'' has only one inversion (E and D)---it is nearly sorted---while the sequence ``ZWQM'' has 6 inversions (it is as unsorted as can be---exactly the reverse of sorted). You are responsible for cataloguing a sequence of DNA strings (sequences containing only the four letters A, C, G, and T). However, you want to catalog them, not in alphabetical order, but rather in order of ``sortedness'', from ``most sorted'' to ``least sorted''. All the strings are of the same length. Input The first line contains two integers: a positive integer n (0 < n <= 50) giving the length of the strings; and a positive integer m (0 < m <= 100) giving the number of strings. These are followed by m lines, each containing a string of length n. Output Output the list of input strings, arranged from ``most sorted'' to ``least sorted''. Since two strings can be equally sorted, then output them according to the orginal order. Sample Input 10 6 AACATGAAGG TTTTGGCCAA TTTGGCCAAA GATCAGATTT CCCGGGGGGA ATCGATGCAT Sample Output CCCGGGGGGA AACATGAAGG GATCAGATTT ATCGATGCAT TTTTGGCCAA TTTGGCCAAA !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! //By LingCh //2005-3-19 Analysis This is a sort problem. As stated, we may first calculate the inversions of each string, and then sort the strings use their inversion as the sort key.  SourceMemory:88K  Time:0MSLanguage:C++  Result:Accepted                #include<vector>              #include<algorithm>              #include<iostream>                             using namespace std;                             int n,m;                             class Mystring              {              public:                 int length;                 int inv;                 char str[50];                                Mystring():length(0),inv(0)                 {                         str[0]=0;                 }                                Mystring& operator = (const Mystring& s);                                   friend istream& operator >>(istream &is,Mystring &istr);                 friend ostream& operator <<(ostream &os,Mystring &ostr);              };                             istream& operator >>(istream &is,Mystring &istr)              {                 int i,j;                 istr.length=n;                 for(i=0;i<istr.length;i++)                         is>>istr.str[i];                 istr.str[istr.length]=0;                   //here calculate the inversion of this string                 istr.inv=0;                 for(i=0;i<istr.length-1;i++)                 {                         for(j=i+1;j<istr.length;j++)                         {                                if(istr.str[i]>istr.str[j])                                        istr.inv++;                         }                 }                 return is;              }                             Mystring& Mystring::operator = (const Mystring& sr)              {                 if (&sr != this)                 {                         copy(&sr.str[0],&sr.str[length],this->str);                         inv=sr.inv;                         length=sr.length;                 }                  return *this;              }                             ostream& operator <<(ostream &os,Mystring &ostr)              {                 int i;                 for(i=0;i<ostr.length;i++)                         os<<ostr.str[i];                 return os;              }                             //this predicate use the inversion of the string as the sort key              bool MyPre(Mystring s1,Mystring s2)              {                 if(s1.inv<s2.inv)                         return true;                 else                         return false;              }                             int main()              {                 int i;                 cin>>n>>m;                                vector<Mystring> ss;                 for(i=0;i<m;i++)                 {                         Mystring s;                         cin>>s;                         ss.push_back(s);                 }                                sort(ss.begin(),ss.end(),MyPre);                                for(i=0;i<m;i++)                         cout<<ss[i]<<endl;                                //system("pause");              }    

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