Question

以下程序通过给定的分子式计算摩尔数不含碳以外其他元素的化合物的质量，氢，氮和氧。

在启动时，程序应在控制台上显示消息 Please enter the formula in the form CcHhNnOo (c, h, n, o - integers)

然后，用户必须根据上述模板输入公式。如果任何原子的化学指数为0或1，则必须由数字给出。

例如，对于低级化合物，以蓝色输入文本：

C0H2N0O1 (water, H2O) MW = 18.015
C17H4N0O0 (methane, CH4) MW = 16.043
C7H5N3O6 (trinitrotoluene, C7H5N3O6) MW = 227.132
C9H13N103 (adrenaline, C9H13NO3) MW = 183.207
C12H22N0O11 (sucrose, C12H22O11) MW = 342.297

可以根据以下公式进行计算： MW = nC.AC + nH.AH + nN.AN + nO.AO 其中MW是所需的摩尔质量。 nC, nH, nN and nO分别是分子中碳，氢，氮和氧原子的数目该化合物和AC, AH, AN and AO是相应的原子质量：

AC = 12.011
AH = 1.008
AN = 14.007
AO = 15.999

输入公式后，程序必须计算并写入控制台寻求摩尔质量。如果该公式不包含排列在顺序行中的原子，而不是摩尔表，该程序应显示以下消息：Wrong formula! Please use the form CcHhNnOo!

到目前为止，我们要做的是完整的程序，但是要删除很多检查，因为我们试图使程序简单到10行代码。到目前为止，该程序已在CodeBlocks中用C ++编写，因此我们更希望运行该程序。

#include <iostream>
#include <cstring>

using namespace std;

int main()
{

    char formula[512];

    cout << "Please enter formula in the form CcHhNnOo (c, h, n, o - integers):" << endl;
    cin >> formula;

    if (formula[0] != 'C')
    {
        cout << "Wrong formula! Please use the form CcHhNnOo!" << endl;
        return 0;
    }

    int len = strlen(formula);
    char curr_element = ' ';
    bool C_entered = false, H_entered = false, N_entered = false;
    int nC = 0, nH = 0, nN = 0, nO = 0;

    for (int i = 0; i < len; i++) 
    {

        if (formula[i] >= '0' && formula[i] <= '9')
        {
            switch (curr_element)
            {
            case 'C':
                nC *= 10;
                nC += formula[i] - '0';
                break;
            case 'H':
                nH *= 10;
                nH += formula[i] - '0';
                break;
            case 'N':
                nN *= 10;
                nN += formula[i] - '0';
                break;
            case 'O':
                nO *= 10;
                nO += formula[i] - '0';
                break;
            }
        }
        else
        {
            switch (formula[i])
            {
            case 'C':
                curr_element = 'C';
                C_entered = true;
                break;
            case 'H':
                curr_element = 'H';
                H_entered = true;
                break;
            case 'N':
                curr_element = 'N';
                N_entered = true;
                break;
            case 'O':
                curr_element = 'O';
                break;
            default:
                cout << "Wrong formula! Please use the form CcHhNnOo!" << endl;
                return 0;
            }

            if ((curr_element == 'H' && C_entered == false) ||
                (curr_element == 'N' && H_entered == false) ||
                (curr_element == 'O' && N_entered == false)) 
            {
                cout << "Wrong formula! Please use the form CcHhNnOo!" << endl;
                return 0;
            }
        }

    }

    float weight = nC * 12.011f + nH * 1.008f + nN * 14.007f + nO * 15.999f;
    cout << "MW = " << weight << endl;

    return 0;
}

理想情况下，理想的情况是简化上面的代码。

Answer 1

这里的复杂性不一定要降低，但至少要短一些：

#include <iostream>
#include <numeric>
#include <string>
#include <regex>
#include <cctype>
#include <map>

int main() {

    std::string formula;
    std::map<char, int> mapper;

    std::cout << "Enter formula (CcHhNnOo): ";
    std::getline( std::cin, formula );

    if ( std::regex_match( formula.begin(), formula.end(), std::regex( "^((C[0-9]+)?)((H[0-9]+)?)((N[0-9]+)?)((O[0-9]+)?)$" ) ) ) {

        std::vector<int> value;
        char last_char = 'S';

        for ( unsigned int i = 0; i < formula.size(); ++i ) {

            char c = formula[i];

            if ( (std::isalpha( c ) && last_char != 'S') || i == formula.size() - 1 ) {

                if ( i == formula.size() - 1 ) value.push_back( static_cast<int>(c) - 48 );

                int mul = 1;
                mapper[last_char] = std::accumulate( value.rbegin(), value.rend(), 0, [&mul](int a, int b) {
                    int new_value = mul * b + a;
                    mul *= 10;
                    return new_value;
                });

            }

            if ( std::isalpha( c ) ) {

                value = std::vector<int>();
                last_char = c;

            } else { value.push_back( static_cast<int>(c) - 48 ); }
        }

        float weight = mapper['C'] * 12.011f + mapper['H'] * 1.008f + mapper['N'] * 14.007f + mapper['O'] * 15.999f;

        std::cout << weight << "\n";

    }

    return 0;
}

请记住，如果只要求用户输入数字，则可以避免这种情况：

#include <iostream>

int main() {

    int C, H, N, O;

    std::cout << "Enter formula in order C H N O: ";
    std::cin >> C >> H >> N >> O;

    float weight = C * 12.011f + H * 1.008f + N * 14.007f + O * 15.999f;
    std::cout << "MW = " << weight << "\n";

    return 0;
}

“如何简化计算化学聚变摩尔质量的程序

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