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SphereCollatz.c++
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SphereCollatz.c++
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// --------------------------
// projects/collatz/Collatz.h
// Copyright (C) 2013
// Glenn P. Downing
// --------------------------
//#ifndef Collatz_h
//#define Collatz_h
// --------
// includes
// --------
#include <iostream> // istream, ostream
#include <cassert> // assert
// ------------
// collatz_read
// ------------
/**
* reads two ints into i and j
* @param r a std::istream
* @param i an int by reference
* @param j an int by reference
* @return true if that succeeds, false otherwise
*/
bool collatz_read (std::istream&, int&, int&);
// ------------
// collatz_eval
// ------------
/**
* @param i the beginning of the range, inclusive
* @param j the end of the range, inclusive
* @return the max cycle length in the range [i, j]
*/
int collatz_eval (int, int);
// -------------
// collatz_print
// -------------
/**
* prints the values of i, j, and v
* @param w a std::ostream
* @param i the beginning of the range, inclusive
* @param j the end of the range, inclusive
* @param v the max cycle length
*/
void collatz_print (std::ostream&, int, int, int);
// -------------
// collatz_solve
// -------------
/**
* read, eval, print loop
* @param r a std::istream
* @param w a std::ostream
*/
void collatz_solve (std::istream&, std::ostream&);
//#endif Collatz_h
// ----------------------------
// projects/collatz/Collatz.c++
// Copyright (C) 2013
// Glenn P. Downing
// ----------------------------
// --------
// includes
// --------
#include <cassert> // assert
#include <iostream> // endl, istream, ostream
#include <string> //for testing purposes
#include <stdio.h>
using namespace std;
//#include "Collatz.h"
// ------------
// collatz_read
// ------------
int cache [1000000];
bool collatz_read (std::istream& r, int& i, int& j) {
r >> i;
if (!r)
return false;
r >> j;
assert(i > 0);
assert(j > 0);
return true;}
// ------------
// collatz_eval
// ------------
int collatz_eval (int i, int j) {
assert(i > 0);
assert(j > 0);
int max = 1;
int temp;
if(i>j)
{
temp = i;
i = j;
j = temp;
}
if(i<(j/2))
i = j/2+1;
for(int a = i; a <= j; a++)
{
int count = 1;
//string q("hello");
int loca = a;
//cout << "cache[" << a << "]: " << cache[a] << endl;
if(cache[a] != 0) //use cache if available
count = cache[a];
else //otherwise, find cycle length
{
while (loca!=1)
{
//cout << "cache[" << loca << "]: " << cache[loca] << endl;
if(loca<1000000)
if(cache[loca] != 0)
{
count = count + cache[loca] - 1; //subtract 1 b/c count was initialized at 1 twice
break;
}
if(loca%2 == 1)
{
loca = loca + (loca>>1) + 1; //odd: (3n+1)/2, 2 steps
count += 2;
}
else
{
loca = loca/2; //even: n/2, 1 step
count++;
}
}
cache[a] = count;
}
if (count > max)
max = count;
assert(max > 0);
}
return max;
}
// -------------
// collatz_print
// -------------
void collatz_print (std::ostream& w, int i, int j, int v) {
assert(i > 0);
assert(j > 0);
assert(v > 0);
w << i << " " << j << " " << v << std::endl;}
// -------------
// collatz_solve
// -------------
void collatz_solve (std::istream& r, std::ostream& w) {
int i;
int j;
while (collatz_read(r, i, j)) {
const int v = collatz_eval(i, j);
collatz_print(w, i, j, v);}}
// -------------------------------
// projects/collatz/RunCollatz.c++
// Copyright (C) 2013
// Glenn P. Downing
// -------------------------------
/*
To run the program:
% g++ -pedantic -std=c++0x -Wall Collatz.c++ RunCollatz.c++ -o RunCollatz
% valgrind RunCollatz < RunCollatz.in > RunCollatz.out
To configure Doxygen:
% doxygen -g
That creates the file "Doxyfile".
Make the following edits:
EXTRACT_ALL = YES
EXTRACT_PRIVATE = YES
EXTRACT_STATIC = YES
GENERATE_LATEX = NO
To document the program:
% doxygen Doxyfile
*/
// -------
// defines
// -------
#ifdef ONLINE_JUDGE
#define NDEBUG
#endif
// --------
// includes
// --------
#include <iostream> // cin, cout, ios_base
//#include "Collatz.h"
// ----
// main
// ----
int main () {
using namespace std;
ios_base::sync_with_stdio(false); // turn off synchronization with C I/O
collatz_solve(cin, cout);
return 0;}