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[Valid_Dark]

these are just quick little programs to solve problems, I named it something short because I had to write it a few times and didn't want to write something longer over and over again, but ya, I need to get into better naming habits.
I won't ever see these programs again, because when I finish I delete it all and start on the next problem using the same Main.cpp file.

[SolarShado]

these are just quick little programs to solve problems, I named it something short because I had to write it a few times and didn't want to write something longer over and over again, but ya, I need to get into better naming habits.
I won't ever see these programs again, because when I finish I delete it all and start on the next problem using the same Main.cpp file.

What environment are you coding in? A good IDE will save you a lot more typing than short names.

[Valid_Dark]

I'm using Code::Blocks

I just got started on problem 11, it looks like a doozy

Spoiler (click to show/hide)

Not a doozy in a hard way, just going to take a little while, also it's my first time working with arrays,
but I've finished the chapter on arrays in my book so I should be more than good.


I have one question though,... why is the plural of Array, arrays ? the plural of cherry isn't cherrys...

[Max White]

Spoiler (click to show/hide)

Well the first thing to realise is that you are being fooled here. There is no 'left' or 'up' because starting from the bottom and going four up gives the same product as starting from the top and going four down. With this in mind, there are only three unique directions you need to check, left to right, top to bottom, and diagonal. These can be done in three separate loops, where as each transverses to the edge of the array minus four in the direction it is checking, and both directions for diagonal. Pretty simple stuff, should be fast to program.

[Levi]

I have one question though,... why is the plural of Array, arrays ? the plural of cherry isn't cherrys...

Programmers are no good at english.   

[Max White]

Arraies? Na, that is redonkulas, let's not use words like 'arraies'.

[Vactor]

Arrays, because we don't call them cherrays

[kaijyuu]

Arrays, because we don't call them cherrays

Well I might start calling them that! What then!?

[Max White]

Arrays, because we don't call them cherrays

No, but we do call them cherries. The idea is that when a word ends in a 'y', you drop it and ad 'ies' to make it plural. Monopoly? Monopolies!

[Valid_Dark]

Just finished problem 11, it took me far too long

Spoiler (click to show/hide)

Code: [Select]

#include <iostream>

using namespace std;

int producth ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row][col+1]*grid[row][col+2]*grid[row][col+3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row][col+1]<<" "<<grid[row][col+2]<<" "<<grid[row][col+3]<<"          "<<product<<endl;
}

int productv ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col]*grid[row+2][col]*grid[row+3][col];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col]<<" "<<grid[row+2][col]<<" "<<grid[row+3][col]<<"          "<<product<<endl;
}

int productd1 ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col+1]*grid[row+2][col+2]*grid[row+3][col+3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col+1]<<" "<<grid[row+2][col+2]<<" "<<grid[row+3][col+3]<<"          "<<product<<endl;
}

int productd2 ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col-1]*grid[row+2][col-2]*grid[row+3][col-3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col-1]<<" "<<grid[row+2][col-2]<<" "<<grid[row+3][col-3]<<"          "<<product<<endl;
}

int main()
{
int answer = 0;
 int grid [20] [20] = {{ 8, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52, 12, 50, 77, 91, 8 },
                                  { 49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00 },
                                  { 81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65 },
                                  { 52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91},
                                  { 22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80},
                                  { 24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50},
                                  { 32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70},
                                  {67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21},
                                  {24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72},
                                  {21, 36, 23, 9, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95},
                                  {78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 9, 53, 56, 92},
                                  {16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57},
                                  {86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58},
                                  {19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40},
                                  {04, 52, 8, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66},
                                  {88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69},
                                  {04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36},
                                  {20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16},
                                  {20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54},
                                  {01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48}};

for ( int x = 0; x<=16;x++)
    for (int y = 0; y <= 20; y++)
            {
            producth(grid,x,y, answer);
           cout << answer<<"   ";
            }

for ( int x = 0; x<=16;x++)
    for (int y = 0; y < 20; y++)
            {
            productv(grid,x,y, answer);
           cout << answer<<"   ";
            }

for ( int x = 0; x<=16;x++)
    for (int y = 0; y <= 16; y++)
            {
            productd1(grid,x,y, answer);
           cout << answer<<"   ";
            }

  for ( int x = 0; x<=16;x++)
    for (int y = 19; y >=3 ; y--)
            {
            productd2(grid,x,y, answer);
           cout << answer<<"   ";
            }

    return answer;
}



I should have written a function to process the array, instead of loading it by hand, would have saved some time...maybe...

[kaenneth]

Spoiler (click to show/hide)

Well the first thing to realise is that you are being fooled here. There is no 'left' or 'up' because starting from the bottom and going four up gives the same product as starting from the top and going four down. With this in mind, there are only three unique directions you need to check, left to right, top to bottom, and diagonal. These can be done in three separate loops, where as each transverses to the edge of the array minus four in the direction it is checking, and both directions for diagonal. Pretty simple stuff, should be fast to program.

are you sure?

Spoiler (click to show/hide)

Does diagonal include cross-diagonal? i.e. "/" and "\" directions?, I would guess so since up and down, left and right, etc. so there should be 4 'loops'

however, I think would do it in 2 loops, but transpose x and y, for checking the 90 degree rotated versions.

[Max White]

Spoiler (click to show/hide)

Good point, I forgot about the other diagonal direction.
As for using only two loops, you are making the assumption that the array has the same width and height. An ideal algorithm would work for an array of any shape and size, and preferably take a parameter for the number of elements to multiply. Gotta be agnostic to your data, you know. 

[kaenneth]

Spoiler (click to show/hide)

Good point, I forgot about the other diagonal direction.
As for using only two loops, you are making the assumption that the array has the same width and height. An ideal algorithm would work for an array of any shape and size, and preferably take a parameter for the number of elements to multiply. Gotta be agnostic to your data, you know. 

Nah, just pad the other dimension with 0's  , but good point.

[Mego]

Arrays, because we don't call them cherrays

No, but we do call them cherries. The idea is that when a word ends in a 'y', you drop it and ad 'ies' to make it plural. Monopoly? Monopolies!

Correct, but only when the letter before the 'y' is a consonant. Hence, monopoly -> monopolies, cherry -> cherries, bay -> bays, array -> arrays.

Just finished problem 11, it took me far too long

Spoiler (click to show/hide)

Code: [Select]

#include <iostream>

using namespace std;

int producth ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row][col+1]*grid[row][col+2]*grid[row][col+3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row][col+1]<<" "<<grid[row][col+2]<<" "<<grid[row][col+3]<<"          "<<product<<endl;
}

int productv ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col]*grid[row+2][col]*grid[row+3][col];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col]<<" "<<grid[row+2][col]<<" "<<grid[row+3][col]<<"          "<<product<<endl;
}

int productd1 ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col+1]*grid[row+2][col+2]*grid[row+3][col+3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col+1]<<" "<<grid[row+2][col+2]<<" "<<grid[row+3][col+3]<<"          "<<product<<endl;
}

int productd2 ( int grid[20][20], int row, int col, int& best)
{
    int product;
   product = grid[row][col]*grid[row+1][col-1]*grid[row+2][col-2]*grid[row+3][col-3];
   if (product > best)
   best = product;
   cout<<grid[row][col]<<" "<<grid[row+1][col-1]<<" "<<grid[row+2][col-2]<<" "<<grid[row+3][col-3]<<"          "<<product<<endl;
}

int main()
{
int answer = 0;
 int grid [20] [20] = {{ 8, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52, 12, 50, 77, 91, 8 },
                                  { 49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 04, 56, 62, 00 },
                                  { 81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 03, 49, 13, 36, 65 },
                                  { 52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56, 71, 37, 02, 36, 91},
                                  { 22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80},
                                  { 24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50},
                                  { 32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70},
                                  {67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21},
                                  {24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72},
                                  {21, 36, 23, 9, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33, 97, 34, 31, 33, 95},
                                  {78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16, 14, 9, 53, 56, 92},
                                  {16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54, 24, 36, 29, 85, 57},
                                  {86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58},
                                  {19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 04, 89, 55, 40},
                                  {04, 52, 8, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66},
                                  {88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69},
                                  {04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36},
                                  {20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 04, 36, 16},
                                  {20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 05, 54},
                                  {01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 01, 89, 19, 67, 48}};

for ( int x = 0; x<=16;x++)
    for (int y = 0; y <= 20; y++)
            {
            producth(grid,x,y, answer);
           cout << answer<<"   ";
            }

for ( int x = 0; x<=16;x++)
    for (int y = 0; y < 20; y++)
            {
            productv(grid,x,y, answer);
           cout << answer<<"   ";
            }

for ( int x = 0; x<=16;x++)
    for (int y = 0; y <= 16; y++)
            {
            productd1(grid,x,y, answer);
           cout << answer<<"   ";
            }

  for ( int x = 0; x<=16;x++)
    for (int y = 19; y >=3 ; y--)
            {
            productd2(grid,x,y, answer);
           cout << answer<<"   ";
            }

    return answer;
}



Quick tip from someone else who does Project Euler: Later on, you'll start encountering problems where the data is given to you as text files. Master file I/O now before you get to them. The header you'll be needing is fstream, with the std::ifstream class for reading and std::ofstream for writing. They work very similarly to std::cin and std::cout.

Why is that, do you ask? Well, std::cin is an object of the std::istream class, of which std::ifstream is a derived class, and std::cout is an object of the std::ostream class, of which std::ofstream is a derived class. The whole std::ios (input/output stream) class hierarchy is pretty crazy.

Spoiler (click to show/hide)

Yes, it involves multiple inheritance. Suck it, Java!

There is one issue with this diagram, though. class std::iostream is in <iostream>, not <istream>. Otherwise, this diagram is accurate.

[Valid_Dark]

I know all about file I/O
used binary file I/O in my game I made
well, maybe not ALL about it, but I've used it before and am plenty comfortable with it.