codeforce 621D - Rat Kwesh and Cheese

题意：求表达式中最大的值。

long double 128位 有效数字18-19 范围正负1.2*10^4932

注意取对数！

 #include<iostream>
 #include<string>
 #include<algorithm>
 #include<cstdlib>
 #include<cstdio>
 #include<set>
 #include<map>
 #include<vector>
 #include<cstring>
 #include<stack>
 #include<cmath>
 #include<queue>
 #include <bits/stdc++.h>
 using namespace std;
 #define INF 0x3f3f3f3f
 #define ll long long
 #define clc(a,b) memset(a,b,sizeof(a))
 const int maxn=;

 const char s[][]=
 {
     "x^y^z",
     "x^z^y",
     "(x^y)^z",
     "(x^z)^y",
     "y^x^z",
     "y^z^x",
     "(y^x)^z",
     "(y^z)^x",
     "z^x^y",
     "z^y^x",
     "(z^x)^y",
     "(z^y)^x"
 };

 int main()
 {
     long double a[];
     long double x,y,z;
     cin>>x>>y>>z;
     a[]=pow(y,z)*log(x);
     a[]=pow(z,y)*log(x);
     a[]=a[]=y*z*log(x);
     a[]=pow(x,z)*log(y);
     a[]=pow(z,x)*log(y);
     a[]=a[]=x*z*log(y);
     a[]=pow(x,y)*log(z);
     a[]=pow(y,x)*log(z);
     a[]=a[]=x*y*log(z);
     int pos=;
     for(int i=; i<=; i++)
     {
         if(a[i]>a[pos])
             pos=i;
     }
     printf("%s\n",s[pos]);
     return ;
 }