I'm currently writing a tetris in C++ and I am at the last stage, I need to delete a row when it is full. Once a piece falls it is stored in a boolean array grid[20][10]. For example I check which row is full (or true), if it is I call a method deleteRow, where n is a number of row:
void Grid::deleteRow(int n)
{
for (j = 0; j < WIDTH; j++)
{
grid[n][j] = false;
}
}
Once the row is deleted I call a method moveRowDown:
void Grid::moveRowDown()
{
for (i = 0; i < HEIGHT; i++)
{
for (j = 0; j < WIDTH; j++)
{
grid[i+1][j]=grid[i][j];
}
}
}
So this method does not work, and all of the pieces disappear. I know I am missing the logic. Thanks for the help in advance!
They disappear because you copy 1st empty row to 2nd, then to 3rd and etc.
You need to rewrite your first loop in Grid::moveRowDown() to work from the bottom of a glass:
for (i = HEIGHT-2; i>=0; i--)
Related
I've tried many methods and this one is one of them:
void init_table(int _table[][MAX_COLUMNS]) {
for (int i = 0; i < MAX_COLUMNS; i++) {
for (int j = 0; j < MAX_ROWS; j++) {
_table[i][j] = -1;
}
}
}
I am just trying to figure out how to initialize my array with -1 rather than 0 it defaults to.
If you need to fill by the same value, use std::fill:
std::fill(_table, _table + MAX_ROWS*MAX_COLUMNS, -1);
Of course, if you use padding or other advanced techniques, you should take this into account and adjust your code, but this is more advanced topics and should be considered separately.
I'm making Sudoku validater program that checks whether solved sudoku is correct or not, In that program i need to compare multiple variables together to check whether they are equal or not...
I have provided a snippet of code, what i have tried, whether every su[][] has different value or not. I'm not getting expecting result...
I want to make sure that all the values in su[][] are unequal.
How can i achieve the same, what are mistakes in my snippet?
Thanks...
for(int i=0 ; i<9 ;++i){ //for checking a entire row
if(!(su[i][0]!=su[i][1]!=su[i][2]!=su[i][3]!=su[i][4]!=su[i][5]!=su[i][6]!=su[i][7]!=su[i][8])){
system("cls");
cout<<"SUDOKU'S SOLUTION IS INCORRECT!!";
exit(0);
}
}
To check for each column uniqueness like that you would have to compare each element to the other ones in a column.
e.g.:
for (int i = 0; i < 9; ++i) {
for (int j = 0; j < 9; ++j) {
for (int k = j + 1; k < 9; ++k) {
if (su[i][j] == su[i][k]) {
system("cls");
cout << "SUDOKU'S SOLUTION IS INCORRECT!!\n";
exit(0);
}
}
}
}
Since there are only 8 elements per row this cubic solution shouldn't give you much overhead.
If you had a higher number N of elements you could initialize an array of size N with 0 and transverse the column. For the i-th element in the column you add 1 to that elements position in the array. Then transverse the array. If there's a position whose value is different from 1, it means you have a duplicated value in the column.
e.g.:
for (int i = 0; i < N; ++i) {
int arr[N] = {0};
for (int j = 0; j < N; ++j)
++arr[su[i][j] - 1];
for (int i = 0; i < N; ++i) {
if (arr[i] != 1) {
system("cls");
cout << "SUDOKU'S SOLUTION IS INCORRECT!!\n";
exit(0);
}
}
}
This approach is way more faster than the first one for high values of N.
The codes above check the uniqueness for each column, you would still have to check for each row.
PS: I have not tested the codes, it may have a bug, but hope you get the idea.
I am trying to create a function that will find the intersection of two dynamically allocated arrays comparing array 1 to array 2. For any values in array 1 that are not in array 2, those values should be deleted in array 1 so that array 1 now only holds the common values of both arrays (no repeats). I cannot use vectors, hashes, or any other thing outside of my current functions in my class:
here is my code so far:
bool IntSet::contains(int val) const
{
for (int i = 0; i < numValues; i++)
{
if (set[i] == val)
return true;
}
return false;
}
this function compares an integer parameter to values currently stored in the array...if a value is in the array it returns true and if else false;
this next function takes in a value and removes that value from the array:
void IntSet::remove(int val)
{
for (int i = 0; i < numValues; i++)
{
if (set[i] == val)
for (int j = 0; j < numValues; j++)
set[j] = set[j + 1];
}
numValues--;
}
here's where I've been having problems, this next function is supposed to iterate through one array and compare those values with the values in the other array...if one value from one array is in the other, it should just skip it, but if a value is not in the array calling the function, it should delete that value from the calling array:
void IntSet::removeDifferent(const IntSet &set2)
{
for (int i = 0; i < set2.size(); i++)
{
if (!set2.contains(set[i]))
{
remove(set[i]);
}
}
}
ive tried about 50 different variations on the removeDifferent() function and I just can't seem to figure this one out. Could someone point me in the right direction?
You're iterating i through the indexes of set2, but then you're testing set[i]. Try this:
void IntSet::removeDifferent(const IntSet &set2)
{
for (int i = 0; i < numValues; ) {
if (!set2.contains(set[i])) {
remove(set[i]);
} else {
i++;
}
}
Note that I also removed i++ from the for loop header. This is because when you remove an element, all the following elements are shifted down, so the next element takes its place in the array. If you incremented i, it would skip that element.
You also need to fix remove. It should start its inner loop from i, so it only shifts down the elements after the one being removed, and it should stop at numValues-1, so it doesn't try to access outside the array when it copies set[j+1]. And as an optimization, it can break out of the outer loop once it has found a match (I assume IntSet doesn't allow duplicates, since you only decrement numValues by 1).
void IntSet::remove(int val)
{
for (int i = 0; i < numValues; i++)
{
if (set[i] == val) {
for (int j = i; j < numValues - 1; j++) {
set[j] = set[j + 1];
}
break;
}
}
numValues--;
}
Your problem is in your remove() function:
void IntSet::remove(int val)
{
for (int i = 0; i < numValues; i++)
{
if (set[i] == val)
for (int j = 0; j < numValues; j++)
set[j] = set[j + 1];
}
numValues--;
}
You can figure out yourself why this is wrong by using a paper and pencil here. Start with a typical example: let's say you found the value you're looking for in the third element of a five-element array:
if (set[i] == val)
In this example, i would be set to 2, and numValues would be set to five. It doesn't matter what val is. Whatever it is, you found it when i is 2, and numValues is five: you found it in the third element of a five element array. Keep that in mind.
Now, you know that you are now supposed to remove the third element in this five element array. But what do you think will happen next:
for (int j = 0; j < numValues; j++)
set[j] = set[j + 1];
Well, using the aforementioned paper and pencil, if you work it out, the following will happen:
set[1] will be copied to set[0]
set[2] will be copied to set[1]
set[3] will be copied to set[2]
set[4] will be copied to set[3]
set[5] will be copied to set[4]
There are two problems here:
A) There is no set[5]. Recall that this is a five-element array, si you only have set[0] through set[4]
B) You're not supposed to copy everything in array down to one element. You have to copy only the elements after the element you want to remove.
Fix these two problems, and you will probably find that everything will work correctly.
I'm trying to create a C++ function which controls if N rectangles are collisioning. The N rectangles are in a std::vector. The idea is to compare every element of the vector with others (only one time) to verify if there are collisions.
I already implemented code to do this, but I am looking for a better, cleaner and more elegant way (I'm a C++ newbie).
My code is:
bool areCollisioningNRectangles(std::vector<Rectangle> rect) {
const unsigned long size = rect.size();
for (int i = 0; i < size - 1; i++) {
for (int j = i + 1; j < size; j++) {
if (areCollisioningTwoRectangles(rect[i], rect[j])) {
return true;
}
}
}
return false;
}
I've been studying this tetris tutorial and I've come across the function that deletes lines and brings the row/s down one level. I'm kind of understanding what is going on with these functions, but some parts are confusing me. I'll try and explain it best I can, but here is the link to the lesson if you need it: http://javilop.com/gamedev/tetris-tutorial-in-c-platform-independent-focused-in-game-logic-for-beginners/
This, to me, looks like a function to get the array to start at the last number of a line:
void Board::DeleteLine (int pY)
{
// Moves all the upper lines one row down
for (int j = pY; j > 0; j--)
{
for (int i = 0; i < BOARD_WIDTH; i++)
{
mBoard[i][j] = mBoard[i][j-1];
}
}
}
Then, there is the function that is causing me problems, which I will explain:
void Board::DeletePossibleLines ()
{
for (int j = 0; j < 20; j++)
{
int i = 0;
while (i < 10)
{
if (mBoard[i][j] != 1) break;
i++;
}
if (i == 10) DeleteLine (j);
}
}
In case you're not familiar, the idea here is to delete a row that consists entirely of 1. But if (mBoard[i][j] != 1) break; would stop the loop if the first line wasn't 1. How would the loop reach a 1 that is somewhere in the middle of the mBoard[][] array if break stops it from doing anything possible straight away?
Am I missing something here? This is my interpretation of it. Perhaps somebody sees something I do't?
Edit:
Thanks for the replies, appreciated.
You could structure the code like this aswell:
for (int j = 0; j < 20; j++)
{
int i = 0;
while (i < 10)
{
if (mBoard[i][j] != 1)
{
break; //only breaks the while loop and will continue with if (i == 10)
}
else
{
i++;
}
}
if (i == 10)
{
DeleteLine (j);
}
}
Now you can clearly see, that the break; is only interrupting your while loop but not your for loop.
The break will jump out of the while loop. So if you encounter a line which has a non-1 somewhere in the middle, i will be the index in the line, and the for loop will continue with the next line (j), starting with i=0 again.
break only interrupts one loop, the while loop in your case. The for loop continues happily.
On a side note, this while could easily (and should) be refactored into a for, and can be compacted according to its recognizable for-if-break pattern :
for (int j = 0; j < 20; ++j)
{
int i;
for(i = 0; i < 10 && mBoard[i][j] == 1; ++i);
if (i == 10) DeleteLine (j);
}