hdu--5135--Greedy

Try to select 3 sticks with a large number of sides to form a triangle until you can select it.

It's easier to calculate the triangle area here or use Helen's formula.

1#include <iostream>2#include <algorithm>3#include <cmath>4#include <cstring>5#include <iomanip>6 using namespacestd;7 8 DoubleAbs (Doublex)9 {Ten     returnx>=0? X:-x; One } A  - Doublea[ the]; - BOOLvis[ the]; the  - intMain () - { -Cin.sync_with_stdio (false); +     intN; -     Doublex, y, z, ans; +      while(Cin >> N &&N) A     { at          for(inti =0; I<n; i++ ) -         { -CIN >>A[i]; -         } -memset (Vis,false,sizeof(Vis)); -Sort (A, A +n); inAns =0; -          for(inti = n1; i>=2; i-- ) to         { +             if( !Vis[i]) -             { thex =A[i]; *y = z =-1; $                 intj = I1;Panax Notoginseng                  while(j>=0 ) -                 { the                     if( !Vis[j]) +                     { Ay =A[j]; the                          Break; +                     } ---J; $                 } $                 intK = J1; -                  while(k>=0 ) -                 { the                     if( !Vis[k]) -                     {Wuyiz =A[k]; the                          Break; -                     } Wu--K; -                 } About                 if(y!=-1&& z!=-1&& y+z>x) $                 { -                     DoubleMid = (x + y + z)/2; -Ans + = sqrt (Mid * ABS (MID-X) * ABS (MID-Y) * ABS (mid-z)); -Vis[i] = vis[j] = Vis[k] =true; A                 } +             } the         } -cout << Setiosflags (iOS::fixed); $cout << Setprecision (2) << ans <<Endl; the     } the     return 0; the}

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hdu--5135--Greedy