1.cpp

24点游戏

/*问题描述：
随意输入4个整数（1－10），用+、-、/、*求出24的算法。*/ 
//by starfish of csdn
#include <iostream>
#include <string>
#include <cmath>
#include <conio.h>
using namespace std;

const double PRECISION = 1E-6;
const int COUNT_OF_NUMBER  = 4;
const int NUMBER_TO_BE_CAL = 24;

double number[COUNT_OF_NUMBER];
string expression[COUNT_OF_NUMBER];

bool Search(int n)
{
    if (n == 1) {
        if ( fabs(number[0] - NUMBER_TO_BE_CAL) < PRECISION ) {
            cout << expression[0] << endl;
            return true;
        } else {
            return false;
        }
    }

    for (int i = 0; i < n; i++) {
        for (int j = i + 1; j < n; j++) {
            double a, b;
            string expa, expb;

            a = number[i];
            b = number[j];
            number[j] = number[n - 1];

            expa = expression[i];
            expb = expression[j];
            expression[j] = expression[n - 1];

            expression[i] = '(' + expa + '+' + expb + ')';
            number[i] = a + b;
            if ( Search(n - 1) ) return true;
            
            expression[i] = '(' + expa + '-' + expb + ')';
            number[i] = a - b;
            if ( Search(n - 1) ) return true;
            
            expression[i] = '(' + expb + '-' + expa + ')';
            number[i] = b - a;
            if ( Search(n - 1) ) return true;
                        

            expression[i] = '(' + expa + '*' + expb + ')';
            number[i] = a * b;
            if ( Search(n - 1) ) return true;

            if (b != 0) {
                expression[i] = '(' + expa + '/' + expb + ')';
                number[i] = a / b;
                if ( Search(n - 1) ) return true;
            } 
            if (a != 0) {
                expression[i] = '(' + expb + '/' + expa + ')';
                number[i] = b / a;
                if ( Search(n - 1) ) return true;
            }

            number[i] = a;
            number[j] = b;
            expression[i] = expa;
            expression[j] = expb;
        }
    }
    return false;
}

void main()
{
	cout<<"请输入4个数:"<<endl;
    for (int i = 0; i < COUNT_OF_NUMBER; i++) {
        char buffer[20];
        int  x;
        cin >> x;
        number[i] = x;
        itoa(x, buffer, 10);
        expression[i] = buffer;
    }

    if ( Search(COUNT_OF_NUMBER) ) {
        cout << "Success." << endl;
    } else {
        cout << "Fail." << endl;
    }        
    getch();
}