Usaco sorting a three-valued Sequence

The main idea: to give you a 1 2 3 sequence, you can sort, to exchange any two elements at a time, ask the minimum number of exchanges

Idea: Greedy, first row 1, if 1 is already in position, then do not move, if it is 2 that and the front of the 1 exchange, if 3, then and the back of the 1 exchange

1 /*{2 id:a42984423 Prob:sort34 lang:c++5 }6 */7#include <iostream>8#include <fstream>9 #defineMAXN 5000Ten using namespacestd; OneIfstream Fin ("sort3.in"); AOfstream Fout ("Sort3.out"); - //#define FIN CIN - //#define Fout cout the intA[MAXN],LISTONE[MAXN]; - intMain () - { -     intN,one=0, two=0, three=0, h=0, r=0, l=0, ans=0; +Fin>>N; -      for(intI=1; i<=n;i++) +     { AFin>>A[i]; at         if(a[i]==1) one++,listone[++r]=i; -         if(a[i]==2) two++; -         if(a[i]==3) three++; -     } -      for(intI=1; i<=one;i++)if(a[i]==1) l++; -      for(intI=1; i<=one;i++) in     { -         if(a[i]==1)Continue; to         Else if(a[i]==2) +         { -Swap (a[i],a[listone[++L]]); theans++; *         } $         Else if(a[i]==3)Panax Notoginseng         { -Swap (a[i],a[listone[r--]]); theans++; +         } A     } the      for(intI=one+1; i<=one+two;i++) +     { -         if(a[i]==3) ans++; $     } $fout<<ans<<Endl; -     return 0; -}

Usaco sorting a three-valued Sequence