Get the exit of maze using stack in C - c

I have an algorithm that search for a exit of a maze using recursive function , how i pass this to a function without recursive but using stack?What this algorithm do is basically , try to found the exit of a matriz , if the next step is 0 or if has already been covered comeback and try another path, but a i need to change the recursive function to a function using stack instead of recursion how i do that?
void print_maze(char **maze, int width, int height) {
for (int i=0; i<13; i++ ){
for (int j=0; j<10; j++ )
{
printf ("%d", maze[i][j]);
}
printf("\n");
}
}
int maze(int x_current, int y_current,char **mazeHere, int height,int width)
{
if (x_current < 0 || x_current >= width || y_current < 0 || y_current >= height)
return 0;
char here = mazeHere[x_current][y_current];
if (here == 3)
return 1;
if(here == 0 || here == 2)
return 0;
mazeHere[x_current][y_current] = 2;
if(maze(x_current ,y_current-1,mazeHere,height,width))return 1;
if(maze(x_current+1,y_current,mazeHere,height,width))return 1;
if(maze(x_current,y_current+1,mazeHere,height,width))return 1;
if(maze(x_current-1,y_current,mazeHere,height,width))return 1;
else{ mazeHere[x_current][y_current] = 1;
return 0;
}
}
int main(void)
{
char matriz [13][10]={
{0,0,0,0,0,0,0,0,0,0},
{0,0,1,1,1,1,1,0,0,0},
{0,0,1,0,0,0,1,0,0,0},
{0,0,1,0,0,0,1,0,0,0},
{1,1,1,0,1,1,1,1,1,0},
{0,1,0,0,1,0,0,0,0,0},
{0,1,1,0,1,1,1,0,0,0},
{0,0,1,0,1,0,0,0,1,0},
{0,0,1,0,0,0,1,1,1,0},
{0,0,1,1,1,1,1,0,0,0},
{0,0,0,0,0,0,1,0,0,0},
{0,0,0,0,0,0,1,1,1,3},
{0,0,0,0,0,0,0,0,0,0},};
int b= 0;
int height = 10;
int width = 13;
int p = 0;
int o = 0;
char **a = malloc(width * sizeof(char*));
for(int x = 0; x< width; x++){
a[x] = malloc(height * sizeof(char));
}
for (int i=0; i<13; i++ ){
for (int j=0; j<10; j++ )
{
a[i][j]= matriz[i][j];
}
}
int res = maze(4,0,a,height,width);
puts(res ? "success!" : "no luck!");
print_maze(a, width, height);
return 0;
}

I understand it's hard without recursion. By the way, conversion from recursion into using stack is not so hard, if you wrote code of stack data structure and its operation. We are going to pursue the matter on the assume.
Recursive function basically has structure like this:
position *seek(position *now, type arg...){
...
if(condition){
return NULL;
} else {
now->next = seek(arg_next);
}
}
It's OK to understand just with your feeling. What it does here is chaining new result to results until now. In other words, storing results as data structure. Here, data structure changes to stack. Then...:
void seek(stack *stack, type arg...){
...
while(1){
if(condition){
break;
} else {
stack->push(next_result)
}
}
}
It's so easy! All that is left is increasing conditions and considering backtracking. Based on the above, try to rewrite your code!

Related

Sorting a structure

I wanted to sort this problem in C with something like bubble sort ... anyone can help
Implement a list with 5 struct Point (Being this a point w/ X, y);
Sort the 5 struct point (first evaluate x then y).
Example:
// The points
p[0]={2,3}
p[1]={4,5}
p[2]={1,5}
p[3]={4,3}
p[4]={1,2}
// Should become
p[0]={1,2}
p[1]={1,5}
p[2]={2,3}
p[3]={4,3}
p[4]={4,5}
If you want to sort structures, you still have to break it down into comparing numeric types. With this in mind, let's take your example with the points:
struct tagPoint
{
int x;
int y;
};
typedef struct tagPoint Point;
Now, let's suppose you have an array of Point and you want it sorted. You can take two approaches:
1. Straightforward function which sorts the array:
Just make the function to sort the array:
void SortPointArray(Point* Points, unsigned int n)
{
/* This will sort the points with priority on the x and then the y value in ascending order. */
for(unsigned int i = 0; i < n-1; i++)
for(unsigned int j = i+1; j < n; j++)
{
if (Points[i].x > Points[j].x)
{
Point aux = Points[i];
Points[i] = Points[j];
Points[j] = aux;
}
else if ((Points[i].x == Points[j].x) && (Points[i].y > Points[j].y))
{
Point aux = Points[i];
Points[i] = Points[j];
Points[j] = aux;
}
}
}
2. Wrap the algorithm in a generic function and use callbacks for each type you want to sort:
This is a little more complicated, but it will save you some time if you use it frequently. Here, this function uses the same algorithm as the one above, but can sort any types.
void Sort(void* lpArray, unsigned int n, size_t cbSize, int (*Cmp)(void*, void*), void (*Swap)(void*, void*))
{
for(unsigned int i = 0; i < n-1; i++)
for(unsigned int j = i+1; j < n; j++)
/* Cast void* to char* to get rid of warning with pointer arithmetic... */
if ( Cmp( ((char*)lpArray) + i*cbSize, ((char*)lpArray) + j*cbSize) )
Swap( ((char*)lpArray) + i*cbSize, ((char*)lpArray) + j*cbSize );
}
As you can see, it requires 2 more functions passed as parameters. If you want this Sort function to know how to sort the Point array, you must define a Comparrison function and a Swapping function and tell the Sort function to use them.
Here is how i implemented them:
/** This function return 1 if p1 should be swapped with p2. */
int ComparePoints(void* vp1, void* vp2)
{
Point *p1, *p2;
p1 = vp1;
p2 = vp2;
if (p1->x > p2->x)
return 1;
else if ((p1->x == p2->x) && (p1->y > p2->y))
return 1;
return 0;
}
/** This will swap 2 points. */
void SwapPoints(void* vp1, void* vp2)
{
Point p = *(Point*)vp1;
*(Point*)vp1 = *(Point*)vp2;
*(Point*)vp2 = p;
}
How do you use them?
If you only want to use the first SortPointArray function, this is enough:
int main()
{
Point Array[10];
/* Read the points. */
for(unsigned int i = 0; i < 10; i++)
scanf("%d %d", &Array[i].x, &Array[i].y);
SortPointArray(Array, 10);
/*Print the points.*/
for(unsigned int i = 0; i < 10; i++)
printf("%d %d\n", Array[i].x, Array[i].y);
return 0;
}
But if you want to use the generic Sort function (which i recommend only if you have multiple types you want to sort like Points, Lines etc) you have to define the two callbacks (ComparePoints and SwapPoints)
int main()
{
Point Array[10];
/* Read the points. */
for(unsigned int i = 0; i < 10; i++)
scanf("%d %d", &Array[i].x, &Array[i].y);
Sort(Array, 10, sizeof(Point), ComparePoints, SwapPoints);
/*Print the points.*/
for(unsigned int i = 0; i < 10; i++)
printf("%d %d\n", Array[i].x, Array[i].y);
return 0;
}
The OP is asking for a C solution, so here you go:
void bsortDesc(struct yourStruct list[80], int s)
{
int i, j;
struct yourStruct temp;
for (i = 0; i < s - 1; i++)
{
for (j = 0; j < (s - 1-i); j++)
{
if (list[j].marks < list[j + 1].marks)
{
temp = list[j];
list[j] = list[j + 1];
list[j + 1] = temp;
}
}
}
}
Also, here's what I got it from: here.

Conway's Game of Life, Segfault 11

I'm trying to write Conway's game of life in C. This is what I have so far. I'm using pointers to refer to the arrays, which has never caused me problems before, but the function place_cell is causing a segfault.
Here's what I've tried so far:
- I tried making the grid with constants, 100 x 100, and 10 x 10. Modifying
values inside of those constant grids still gives me a segfault.
- I tried using constants for place_cell, still got a segfault.
int** make_grid(int x, int y) {
int** is = (int**)malloc(sizeof(int*) * y);
if(! is) {
fprintf(stderr, "make_grid: malloc failed");
exit(1);
}
int j;
for(j = 0; j < y; j++) {
is[j] = (int*)malloc(sizeof(int) * x);
if(!is[j]) {
fprintf(stderr, "make_grid: malloc failed");
exit(1);
}
}
return is;
}
/* takes two integers and places a cell at those coords */
void place_cell(int** is, int sidex, int sidey, int x, int y) {
if(x >= sidex || y >= sidey) {
fprintf(stderr, "place_cell: out of grid range\n");
exit(1);
}
is[y][x] = 1;
}
int check_surroundings(int** is, int sidex,
int sidey, int x, int y) {
int y_less = y - 1;
if(y == 0) {
y_less = sidey - 1;
}
int y_more = y + 1;
if(y == sidey - 1) {
y_more = 0;
}
int x_less = x - 1;
if(x == 0) {
x_less = sidex - 1;
}
int x_more = x + 1;
if(x == sidex - 1) {
x_more = 0;
}
int p = is[y_less][x_less] +
is[y_less][x] +
is[y_less][x_more] +
is[y][x_less] +
is[y][x_more] +
is[y_more][x_less] +
is[y_more][x_less] +
is[y_more][x_more];
return p;
}
void change_condition(int** is,
int sidex, int sidey, int x, int y) {
int* state = &is[y][x];
int surr = check_surroundings(is, sidex, sidey, x, y);
if(surr > 3) {
*state = 0;
} else if(surr == 3 || surr == 2) {
*state = 1;
} else {
*state = 0;
}
}
void print_grid(int** is, int sidex, int sidey) {
int i, j;
for(i = 0; i < sidey; i++) {
for(j = 0; j < sidex; j++) {
if(is[i][j] == 1) {
printf("*");
} else {
printf(" ");
}
}
printf("\n");
}
}
void new_generation(int** is, int sidex, int sidey) {
int i, j;
for(i = 0; i < sidey; i++) {
for(j = 0; j < sidex; j++) {
change_condition(is, sidex, sidey, j, i);
}
}
}
void play(int** is, int sidex, int sidey) {
int i = 0;
while(i < 100) {
new_generation(is, sidex, sidey);
print_grid(is, sidex, sidey);
i++;
}
}
here's my main:
int main(int argc, char* argv[]) {
int sidex = atoi(argv[0]);
int sidey = atoi(argv[1]);
int** is = make_grid(10, 10);
int i;
for(i = 2; i < argc; i += 2) {
place_cell(is, sidex, sidey,
atoi(argv[i]), atoi(argv[i + 1]));
}
return 0;
}
edit:
int** make_grid(int x, int y) {
int (*is)[x] = (int*)malloc(sizeof(int) * y * x);
if(! is) {
fprintf(stderr, "make_grid: malloc failed");
exit(1);
}
int j;
for(j = 0; j < y; j++) {
is[j] = (int*)malloc(sizeof(int) * x);
if(!is[j]) {
fprintf(stderr, "make_grid: malloc failed");
exit(1);
}
}
return is;
}
This isn't right at all but I can't put my finger on why. Can someone explain to me what to change like I'm five? (a five year-old who knows C, I guess)
I just copied your entire code and tried to run the program. The memory access violation (at least for me) is in this line:
int sidex = atoi(argv[0]);
int sidey = atoi(argv[1]); <-- memory access violation
The reason is (in my case at least) that I just ran the program with no arguments.
Now, even if I did provide the arguments on the command line the indexing is still off. The first argument argv[0] is the name of the executable, not the first argument after the name.
So, a few things to note for your code:
It is not guaranteed that there will be arguments. You should always check the argc to make sure you can index into argv
Those arguments are not guaranteed to be integer numbers either - you better check for that too, before you use them as your dimensions
Of course with the indexing shift you should adjust for your "array reading" code accordingly as well. But once you fix the indexing this should be an easy one for you
You are not declaring a two-dimensional array with that syntax, so the memory is not aligned the way you think, thus a segmentation fault. Declaring a pointer int** does not make it a 2-D array. (Surely you don't think int *** would get you a data cube ?).
Heap allocate a 2D array (not array of pointers)
One of the comments above gives the other problem, the zero parameter to a C program argv[0] is the name of the program, not the first parameter on the command line, that is argv[1].

Arrays of pointer dereferencing

I want to a function named sortPointers() that sets an array of integer pointers to point to the elements of another array in ascending order.
What I have done so far is
void sortP(int src[], int *ptrs[], int n)
{
int temp;
for(int i = 0; i< n ; i++)
{
ptrs[i] = & src[i]; // assign the address of each number in the src[] to the array of pointers
}
while (1)
{
int flag = 0;
for(int i = 0; i< n;i++)
{
if ( *(ptrs[i]) > *(ptrs[i+1])) //bubble sort
{
temp = *(ptrs[i]);
*(ptrs[i]) = *(ptrs[i+1]);
*(ptrs[i+1]) = temp;
flag = 1;
}
}
if(flag == 0);
break;
}
for(int i = 0; i< n;i++)
{
printf("%i\n",ptrs[i]);
}
}
In main function , I call this function
main()
{
int a[5] = {5,4,3,2,1};
int *ptrs[5]= {&a[0],&a[1],&a[2],&a[3],&a[4]};
sortP(a, *ptrs, 5);
}
My result are addresses, If I want to print out the actual value that the pointers point to (1,2,3,4,5) ,what should I change in the printf()?
THanks
P.S. I try *ptrs[i] before , but I got strange number though , not the ones in src[]..
My result are addresses
Technically, your results are undefined behavior, because %i expects an int, not an int*.
Fixing this problem is simple: add a dereference operator in front of ptrs[i], like this:
for(int i = 0; i< n;i++) {
printf("%i\n", *ptrs[i]);
}
I got strange number though , not the ones in src[]
The real problem with your code is that you are swapping pointers incorrectly. In fact, you can tell that it's incorrect simply by looking at temp: it needs to be int*, not int and the dereferences on the swap need to go away.
see annotations :
void sortP(int src[], int *ptrs[], int n)
{
int temp;
for(int i = 0; i< n ; i++)
{
ptrs[i] = & src[i]; // assign the address of each number in the src[] to the array of pointers
}
while (1)
{
int flag = 0;
// check if i < n-1, not n
for(int i = 0; i< n-1;i++)
{
if ( *(ptrs[i]) > *(ptrs[i+1])) //bubble sort
{
temp = *(ptrs[i]);
*(ptrs[i]) = *(ptrs[i+1]);
*(ptrs[i+1]) = temp;
flag = 1;
}
}
if(flag == 0)
break;
}
for(int i = 0; i< n;i++)
{
//*ptrs[i] instead of ptrs[i]
printf("%i ",*ptrs[i]);
}
}
int main(void)
{
int a[5] = {5,4,3,2,1};
int *ptrs[5];//= {&a[0],&a[1],&a[2],&a[3],&a[4]};
sortP(a, ptrs, 5);
}

Simple c prog. error: invalid type arguement of unary '*'

this is my first post here and I'm very new to C.
I want to write a program that is able to print matrixes. It should look like:
----
-o--
ooo-
----
So i want that to be printed for the beginning.
My current code is:
// 4. Exercise
// Learn 2d arrays
#include <stdio.h>
char z;
char s;
char m1_ptr;
void createMatrix()
{
for(z = 0; z != 4; z++)
{
for (s = 0; s != 4; s++)
{
printf("%c", *m1_ptr);
}
printf("\n");
}
}
//------------------------------------------------------------------
int main()
{
char o = o;
char c = '-';
// And some variables for the matrix count:
char matrix_1 [4][4] ={{c,c,c,c},{c,o,c,c},{o,o,o,c},{c,c,c,c}};
char *m1_ptr = &matrix_1 [z][s];
createMatrix(matrix_1 [0][0]);
/* for(z = 0; z != 4; z++)
{
for (s = 0; s != 4; s++)
{
printf("%c", matrix_1 [z][s]);
}
printf("\n");
}
*/
return 0;
}
It works if I put the void function into the main, but since there are much more matrixes coming I want to do that in an extra function to make it more readable.
If I compile that I get the error message:
"Line17: Error: invalid type argument of unary '*' ('have int')"
(edit: line 17 is where it says "printf("c......")
I looked at other questions, but since I only understand super simple programs yet that didn't work out for me.
Does anyone know how that could be fixed?
(It would be nice if the answer explains why, since I have very little experience with pointers)
I think your looking for something like this:
#include <stdio.h>
#define ROW 4
#define COLUMN 4
void printMatrix(int rowLength, int columnLength, char matrix[rowLength][columnLength]) {
int rowCount, columnCount;
for(rowCount = 0; rowCount < rowLength; rowCount++) {
for(columnCount = 0; columnCount < columnLength; columnCount++)
printf("%c", matrix[rowCount][columnCount]);
printf("\n");
}
}
int main() {
char o = 'o';
char c = '-';
char matrix_1 [ROW][COLUMN] = {
{c,c,c,c},
{c,o,c,c},
{o,o,o,c},
{c,c,c,c}
};
printMatrix(ROW, COLUMN, matrix_1);
return 0;
}
It prints the pattern you want
#include <stdio.h>
void displayMatrix( char pMatrix[rCount][cCount], int rCount, int cCount )
{
for(int i = 0; i < rCount; i++ ) // one loop for each row
{
for (int j = 0; j < cCount; j++) // one loop for each column
{
printf("%c", pMatrix[i][j]);
}
printf("\n"); // prep for next row
}
}
//------------------------------------------------------------------
static const o = 'o';
static const c = '-';
int main()
{
// And some variables for the matrix count:
char matrix_1 [][] ={{c,c,c,c},{c,o,c,c},{o,o,o,c},{c,c,c,c}};
displayMatrix(matrix_1,
sizeof( matrix_1) / sizeof(matrix_1[0]), // = number of rows
sizeof( matrix_1[0]) ); // = number of columns
return 0;
}

C: interleaving with for loop?

I need to create a program which would ask from user to input a string and then function in program needs to separate it to 2 strings of same size (user always inputs even number of chars) and after that it has to "shuffle" them...
So it should basically do this:
user inputs: A1B1C1D1
code should make 2 same sized strings: A1B1 and C1D1 and after that it should "shuffle" them to look like this: A1C1B1D1.
So it needs to take first 2 elements of first string, then first 2 elements of second string and so on…
My problem is that when I input A1B1C1D1, after I run the program, I get AC1BD1 (it leaves out 2nd char from first array).
#include<stdio.h>
#include<string.h>
#define N 100
void shuffle(char *cards) {
int i, n, x=0, c1=0, c2=0, j=0;
char tmp1[N]={0}, tmp2[N]={0};
n=strlen(cards);
//divide to 2 arrays with same number of elements
for(i=0; i<n; i++){
if(i<(n/2)){
tmp1[i]=cards[i];}
else{
tmp2[x]=cards[i];
x++;
}
}
//storing 2 elements from first array, then 2 elements from second array and so on
for(i=0; i<n; i++){
if(j>3){
j=0;
}
if(j<=1){ // store 2 elements from 1st array
cards[i]=tmp1[c1];
c1++;
j++;
}
if(j>=2){ // store 2 elements from 2nd array
cards[i]=tmp2[c2];
c2++;
j++;
}
}
printf("1st half:%s\n2nd half:%s", tmp1, tmp2);
printf("\n\t%s",cards);
return;
}
int main() {
char cards[N];
scanf("%s", cards);
shuffle(cards);
return 0;
}
The problem is here
if(j<=1){ // store 2 elements from 1st array
cards[i]=tmp1[c1];
c1++;
j++;
}
if(j>=2){ // store 2 elements from 2nd array
cards[i]=tmp2[c2];
c2++;
j++;
}
Make the second if as an "else if" (just an "else" is also enough)
What happens is that after you increment j from 1 to 2, you go into the second if statement, and rewrite on the same index on cards.
If you don't mind an alternative suggestion for "shuffling your deck of cards" in a much simpler way:
void shuffle(char *cards)
{
char tmp[N]={0};
int n = strlen(cards);
for (int i=0; i<n/2; i++)
tmp[i*2+0] = cards[i];
for (int i=0; i<n/2; i++)
tmp[i*2+1] = cards[i+n/2];
for (int i=0; i<n; i++)
cards[i] = tmp[i];
}
You call it shuffle and cards.
Wouldnt it be better to make a card structure that has two elements?
I thinky your j in the for loop is behaving wrong.
I will double check this and edit this answer if it wasnt j.
EDIT:
Your cradcount was off by a bit and you wrote the wrong index.
Here is some working code:
j = 0;
i = 0;
while(i<n)
{
++j;
if(j == 1 || j == 2)
{ // store 2 elements from 1st array
cards[i++]=tmp1[c1++];
}
else if(j == 3 || j == 4)
{ // store 2 elements from 2nd array
cards[i++]=tmp2[c2++];
}
else
{
j = 0;
}
}
In general you can use the debugger to see whats happening with your index. I assume this is homework and you have to write "optimal code". In general it would be beneficial to use varaiblaenames with more meaning.
EDIT2:
There is a nice solution below that illustrates time optimized code.
I wanted to add some code that i think is easier to read and maintain.
#include<stdio.h>
#include<string.h>
#define DECK_MAX 100
typedef struct
{
char group;
int number;
}Tcard;
typedef struct
{
Tcard card[DECK_MAX];
int count;
}Tdeck;
int ReadDeck(Tdeck * deck, const char *cardstring);
int DeckAddCopy(Tdeck * deck, Tcard * card);
int PrintDeck(Tdeck * deck, const char *deckname);
int InterleaveDecksCopy(Tdeck * target, Tdeck * source[], int sourcecount);
int SplitDeckCopy(Tdeck * source, Tdeck * target[], int targetcount);
int main() {
int e = 0;
char cardstring[100];
Tdeck deck, stackA, stackB, interleaved;
Tdeck * stacks[] = {&stackA, &stackB};
printf("Please input a cardstring: ");
scanf("%s", cardstring);
e |= ReadDeck(&deck, cardstring);
e |= PrintDeck(&deck, "cardstring");
e |= SplitDeckCopy(&deck, stacks, sizeof(stacks) / sizeof(Tdeck*) );
e |= PrintDeck(&stackA, "1st half");
e |= PrintDeck(&stackB, "2nd half");
e |= InterleaveDecksCopy(&interleaved, stacks, sizeof(stacks) / sizeof(Tdeck*) );
e |= PrintDeck(&interleaved, "interleaved");
if( e != 0) printf("There was an error dureing execution.\n");
return e;
}
int ReadDeck(Tdeck * deck, const char *cardstring)
{
int e = 0;
int varCount, n, total = 0;
Tcard card;
memset(deck, 0, sizeof(Tdeck));
do{
n = 0;
varCount = sscanf(&cardstring[total], "%c%i%n", &card.group, &card.number, &n);
total += n;
if( varCount == 2 )
{
//check if card is valid?
e |= DeckAddCopy(deck, &card);
}
else
{
if(strlen(cardstring) != total)
{
//string was not read completely
e |= 1;
}
}
}while(varCount == 2);
return e;
}
int DeckAddCopy(Tdeck * deck, Tcard * card)
{
int e = 0;
if(deck->count >= DECK_MAX)
{
e |= 1;
}
else
{
memcpy(&deck->card[deck->count++], card, sizeof(Tcard));
}
return e;
}
int PrintDeck(Tdeck * deck, const char *deckname)
{
int c;
printf("%s contains %i cards%s", deckname, deck->count, (deck->count == 0)? ".\n":": ");
for(c = 0; c < deck->count; ++c)
{
printf("%c%i%s", deck->card[c].group, deck->card[c].number, ( c+1 < deck->count) ? ", ":".\n");
}
return 0;
}
int InterleaveDecksCopy(Tdeck * target, Tdeck * source[], int sourcecount)
{
int c, s, e = 0;
memset(target, 0, sizeof(Tdeck));
for(c = 0; c < DECK_MAX; ++c)
{
for(s = 0; s < sourcecount ; ++s)
{
if(c < source[s]->count)
{
e |= DeckAddCopy(target, &source[s]->card[c]);
}
}
}
return e;
}
int SplitDeckCopy(Tdeck * source, Tdeck * target[], int targetcount)
{
int c, t, e = 0;
for(t = 0; t < targetcount ; ++t)
{
memset(target[t], 0, sizeof(Tdeck));
}
c = 0;
for(t = 0; t < targetcount ; ++t)
{
int cMax = (source->count) - (((source->count)/targetcount) * targetcount - t - 1 );
for( ; c < (t+1)*(source->count)/targetcount ; ++c)
{
e |= DeckAddCopy(target[t], &source->card[c]);
}
}
return e;
}

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