Molecules

t12e13.chemicalmolecules.cpp

// t12e13.chemicalmolecules.cpp
// juanfc 2025-11-18 
// Chemical compounds are made of many identical molecules. A molecule consists
// of a sequence (an array) of elements. These elements are atoms (e.g., Fe, H,
// Ni) repeated in the molecule. An  integer indicates how many times that atom
// appears in the molecule. Each element (|TElement|) can therefore be a
// structure storing a string representing the atom (the letter Fe, H, etc.)
// together with its frequency (an integer in the range 1–9). A molecule
// (TMolecule) is then an open array of TElement of these .
// Write a function |TMolecule string2Molec(string s);| that parses the input
// string and returns a |TMolecule| structure.
// Write also a procedure to print them: |void printMol(TMolecule);| in the
// classic way. So |printMol((TMolecule){{"Na", 1}, { "O", 1}, {"H", 1}})| would
// print: |NaOH|

#include <iostream>
#include <array>
using namespace std;

const int N = 100;

struct TElement {
    string elem;
    int n;
};
typedef array<TElement,N> TMolecule;
struct TMulMolec {
    TMolecule m;
    int n;
};

typedef array<TMulMolec,N> TMixMolec;

struct TReaction {
    TMixMolec reactants;
    TMixMolec products;
};



int main()
{
    TMolecule string2Molec(string s);
    void print(TMolecule);

    TMolecule chloricAcid = string2Molec("HCl");
    TMolecule sodiumHidroxide = string2Molec("NaOH");
    print(chloricAcid);
    print(sodiumHidroxide);
    return 0;
}

TMolecule string2Molec(string s)
{
    TMolecule r;
    int last = 0;
    TElement e;
    for (int i = 0; i < s.size(); ++i) {
        if (s[i] >= 'A' and s[i] <= 'Z') {
            // new element, add the previous if any
            if (e.elem != "") {
                r[last++] = e;
            }
            e.elem = s[i];
            e.n = 1;
        } else if (s[i] >= 'a' and s[i] <= 'z') {
            e.elem += s[i];
        } else if (s[i] >= '0' and s[i] <= '9') {
            e.n = s[i] - '0'; // only one digit
        }
    }
    if (e.elem != "") {
        r[last++] = e;
    }
    return r;
}

void print(TMolecule m)
{
    int i = 0;
    while (m[i].elem != "") {
        cout << m[i].elem;
        if (m[i].n > 1)
            cout << m[i].n;
        ++i;
    }
    cout << endl;

}