collatz.cpp

#include <cstdio>
#include <map>

using namespace std;

int getCollatz(long a, map<long,int> &source)
{
    if( source.find(a) == source.end() )
    {
        if(a%2 == 0)
            source[a] = 1 + getCollatz(a/2, source);
        else
            source[a] = 1 + getCollatz(3*a+1, source);
    }
        
    return source[a];
}

int main()
{
    map<long, int> collatz;
    int steps;
    long input;
    collatz[1] = 1;

    while ( scanf("%li", &input) > 0 ){
        steps = getCollatz( input, collatz);
        printf("%li in %d steps.\n", input, steps);