SubmitCollatz.c++

// ----------------------------
// projects/collatz/Collatz.c++
// Copyright (C) 2016
// Glenn P. Downing
// ----------------------------

// --------
// includes
// --------

#include <cassert>  // assert
#include <iostream> // endl, istream, ostream
#include <sstream>  // istringstream
#include <string>   // getline, string
#include <vector>
#include <utility>  // make_pair, pair

using namespace std;

// ------------
// collatz_read
// ------------

pair<int, int> collatz_read (const string& s) {
    istringstream sin(s);
    int i;
    int j;
    sin >> i >> j;
    return make_pair(i, j);}

// ------------
// collatz_eval
// ------------

int collatz_eval (int i, int j) {
    int ans = -1; 
    int count = 1;
    int num;
    if (j < i){
	i ^= j;
	j ^= i;
	i ^= j;
    }
    for(int x = i; x <= j; ++x){
	num = x;
	while(num != 1){
            if ((num & 1) == 0){
		num >>= 1;
	    }
	    else {
       	        num = (num << 1) + num + 1;
	    } 
	    ++count;
        }
        if (count > ans)
 	    ans = count;
        count = 1;
    }
    return ans;
}

// -------------
// collatz_print
// -------------

void collatz_print (ostream& w, int i, int j, int v) {
    w << i << " " << j << " " << v << endl;}

// -------------
// collatz_solve
// -------------

void collatz_solve (istream& r, ostream& w) {
    string s;
    while (getline(r, s)) {
        const pair<int, int> p = collatz_read(s);
        const int            i = p.first;
        const int            j = p.second;
        const int            v = collatz_eval(i, j);
        collatz_print(w, i, j, v);}}

// ----
// main
// ----

int main () {
    using namespace std;
    collatz_solve(cin, cout);
    return 0;}

/*
% g++ -pedantic -std=c++11 -Wall Collatz.c++ RunCollatz.c++ -o RunCollatz



% cat RunCollatz.in
1 10
100 200
201 210
900 1000



% RunCollatz < RunCollatz.in > RunCollatz.out



% cat RunCollatz.out
1 10 1
100 200 1
201 210 1
900 1000 1



% doxygen -g
// That creates the file Doxyfile.
// Make the following edits to Doxyfile.
// EXTRACT_ALL            = YES
// EXTRACT_PRIVATE        = YES
// EXTRACT_STATIC         = YES



% doxygen Doxyfile
// That creates the directory html/.
*/