look and say

t11e24.lookandsay.cpp

// t11e24.lookandsay.cpp
// juanfc 2023-11-22
// 

#include <iostream>
using namespace std;

string lookandsay(string s);

int main()
{

    string previous = "1";
    do {
        string newone = lookandsay(previous);
        cout << previous << endl;
        previous = newone;
    } while (previous.length() <= 20);

    return 0;
}

int reps(string s, int pos);

string lookandsay(string s)
{
    string r;
    int i = 0;

    while (i < s.length()) {
        int cont = reps(s, i);
              r += char(cont + '0');
              r += s[i];
              i += cont;
    }
    return r;
}

int reps(string s, int pos)
{
    int i = 0;
    while (pos+i < s.length() and s[pos+i] == s[pos])
        ++i;
    return i;
}