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-8;
const double PI = atan(1.0)*4;
const int maxint = 2139062143;

int num(int x)
{
    int ret = 0;
    while (x){
        if (x & 1) ++ ret;
        x >>= 1;
    }
    return ret;
}

int gao(int s, int t, int x, int y)
{
    int num = s & 1 ? x : y, times = 0;
    s >>= 1;
    while (times < 3){
        int tmp = s & 1 ? x : y;
        int suan = t % 3;
        if (suan == 0) num = tmp + num;
        else if (suan == 1) num = tmp * num;
        else num = num - tmp;

        s >>= 1; t /= 3;
        ++ times; 
    }
    return num;
}

class CountExpressions
{
    public:
        int calcExpressions(int x, int y, int val){
            int cnt = 0;
            int the = 3 * 3 * 3;
            for (int i = 0; i < (1<<4); ++ i) if (num(i) == 2)
                for (int j = 0; j < the; ++ j)
                    if (gao(i, j, x, y) == val) ++ cnt;
            return cnt;
        }
        
// BEGIN CUT HERE
    public:
    void run_test(int Case) { if ((Case == -1) || (Case == 0)) test_case_0(); if ((Case == -1) || (Case == 1)) test_case_1(); if ((Case == -1) || (Case == 2)) test_case_2(); if ((Case == -1) || (Case == 3)) test_case_3(); if ((Case == -1) || (Case == 4)) test_case_4(); if ((Case == -1) || (Case == 5)) 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 << "	Expected: "" << Expected << '"' << endl; cerr << "	Received: "" << Received << '"' << endl; } }
    void test_case_0() { int Arg0 = 7; int Arg1 = 8; int Arg2 = 16; int Arg3 = 9; verify_case(0, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
    void test_case_1() { int Arg0 = 3; int Arg1 = 5; int Arg2 = 7; int Arg3 = 5; verify_case(1, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
    void test_case_2() { int Arg0 = 99; int Arg1 = 100; int Arg2 = 98010000; int Arg3 = 6; verify_case(2, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
    void test_case_3() { int Arg0 = -99; int Arg1 = 42; int Arg2 = -1764; int Arg3 = 2; verify_case(3, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
    void test_case_4() { int Arg0 = 100; int Arg1 = -100; int Arg2 = -100000000; int Arg3 = 0; verify_case(4, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }
    void test_case_5() { int Arg0 = 1; int Arg1 = 2; int Arg2 = 5; int Arg3 = 17; verify_case(5, Arg3, calcExpressions(Arg0, Arg1, Arg2)); }

// END CUT HERE

};

// BEGIN CUT HERE
int main()
{
//    freopen( "a.out" , "w" , stdout );    
    CountExpressions ___test;
    ___test.run_test(-1);
       return 0;
}
// END CUT HERE