SRM 398(1-250pt)

题意：有两个变量x和y，三种运算符+,*,-，组成等式"变量 运算符 变量 运算符 变量 运算符 变量"，要求每个变量恰好出现两次，且等式的值为val的等式有多少个。注意不计算运算符的优先级，比如2+2*3先计算2+2，最终结果得12。

解法：暴力即可。O(2^4 * 3^3)。终于交到200pt了...

tag:brute-force

 // BEGIN CUT HERE
 /*
  * Author:  plum rain
  * score :
  */
 /*

  */
 // END CUT HERE
 #line 11 "CountExpressions.cpp"
 #include <sstream>
 #include <stdexcept>
 #include <functional>
 #include <iomanip>
 #include <numeric>
 #include <fstream>
 #include <cctype>
 #include <iostream>
 #include <cstdio>
 #include <vector>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 #include <cstdlib>
 #include <set>
 #include <queue>
 #include <bitset>
 #include <list>
 #include <string>
 #include <utility>
 #include <map>
 #include <ctime>
 #include <stack>

 using namespace std;

 #define CLR(x) memset(x, 0, sizeof(x))
 #define CLR1(x) memset(x, -1, sizeof(x))
 #define PB push_back
 #define SZ(v) ((int)(v).size())
 #define ALL(t) t.begin(),t.end()
 #define zero(x) (((x)>0?(x):-(x))<eps)
 #define out(x) cout<<#x<<":"<<(x)<<endl
 #define tst(a) cout<<#a<<endl
 #define CINBEQUICKER std::ios::sync_with_stdio(false)

 typedef vector<int> VI;
 typedef vector<string> VS;
 typedef vector<double> VD;
 typedef pair<int, int> pii;
 typedef long long int64;

 const double eps = 1e-;
 const double PI = atan(1.0)*;
 const int maxint = ;

 int num(int x)
 {
     int ret = ;
     while (x){
         if (x & ) ++ ret;
         x >>= ;
     }
     return ret;
 }

 int gao(int s, int t, int x, int y)
 {
     int num = s &  ? x : y, times = ;
     s >>= ;
     while (times < ){
         int tmp = s &  ? x : y;
         int suan = t % ;
         if (suan == ) num = tmp + num;
         else if (suan == ) num = tmp * num;
         else num = num - tmp;

         s >>= ; t /= ;
         ++ times;
     }
     return num;
 }

 class CountExpressions
 {
     public:
         int calcExpressions(int x, int y, int val){
             int cnt = ;
             int the =  *  * ;
             for (int i = ; i < (<<); ++ i) if (num(i) == )
                 for (int j = ; j < the; ++ j)
                     if (gao(i, j, x, y) == val) ++ cnt;
             return cnt;
         }

 // BEGIN CUT HERE
     public:
     void run_test(int Case) { if ((Case == -) || (Case == )) test_case_0(); if ((Case == -) || (Case == )) test_case_1(); if ((Case == -) || (Case == )) test_case_2(); if ((Case == -) || (Case == )) test_case_3(); if ((Case == -) || (Case == )) test_case_4(); if ((Case == -) || (Case == )) test_case_5(); }
     private:
     template <typename T> string print_array(const vector<T> &V) { ostringstream os; os << "{ "; for (typename vector<T>::const_iterator iter = V.begin(); iter != V.end(); ++iter) os << '\"' << *iter << "\","; os << " }"; return os.str(); }
     void verify_case(int Case, const int &Expected, const int &Received) { cerr << "Test Case #" << Case << "..."; if (Expected == Received) cerr << "PASSED" << endl; else { cerr << "FAILED" << endl; cerr << "\tExpected: \"" << Expected << '\"' << endl; cerr << "\tReceived: \"" << Received << '\"' << endl; } }
     void test_case_0() { int Arg0 = ; int Arg1 = ; int Arg2 = ; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
     void test_case_1() { int Arg0 = ; int Arg1 = ; int Arg2 = ; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
     void test_case_2() { int Arg0 = ; int Arg1 = ; int Arg2 = ; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
     void test_case_3() { int Arg0 = -; int Arg1 = ; int Arg2 = -; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
     void test_case_4() { int Arg0 = ; int Arg1 = -; int Arg2 = -; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
     void test_case_5() { int Arg0 = ; int Arg1 = ; int Arg2 = ; int Arg3 = ; verify_case(, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }

 // END CUT HERE

 };

 // BEGIN CUT HERE
 int main()
 {
 //    freopen( "a.out" , "w" , stdout );
     CountExpressions ___test;
     ___test.run_test(-);
        return ;
 }
 // END CUT HERE