What is corrupting the stack of this multidimensional array? - c++

Question

This script produces a fibonacci spiral which starts off in the centre and branches outward. Although the output is correct, i get an error message saying:
"Run-Time Check Failure #2 - Stack around the variable 'fibArr' was corrupted."
I've tried reducing fibCount by 1, but this caused the central number to be 0 which I dont want.
int fibFunc(int);
int main() {
//--setting variables
const int rowCount = 5, colCount = 5;
const int fibCount = rowCount * colCount - 1;
static int f;
int i, j;
//--creating grid
int grid[rowCount][colCount] = { 0 };
//Create fibArr
f = fibCount;
int fibArr[fibCount];
while (f >= 0) {
fibArr[f] = fibFunc(f);
f--;
}
//directions settings
enum direction {
DOWN, RIGHT, UP, LEFT
} d = DOWN;
//spiral loop
int R = 0, C = 0; //R for row, C for column
f = fibCount;
while (f >= 0) {
grid[R][C] = fibArr[f];
f--;
if (d == DOWN) {
if (grid[R+1][C] == 0)
R++;
else d = RIGHT;
}
if (d == RIGHT) {
if (grid[R][C+1] == 0)
C++;
else d = UP;
}
if (d == UP) {
if (grid[R-1][C] == 0)
R--;
else d = LEFT;
}
if (d == LEFT) {
if (grid[R][C-1] == 0)
C--;
else {
d = DOWN;
R++;
}
}
}
printFib(fibArr, fibCount);
for (i = 0; i < rowCount; i++) {
for (j = 0; j < colCount; j++) {
cout << setw(7) << grid[i][j];
}
cout << endl;
cout << endl;
}
system("pause>nul");
}
int fibFunc(int n) {
if (n == 0 || n == 1)
return 1;
else
return fibFunc(n - 1) + fibFunc(n - 2);
}
Output
75025 55 89 144 233
46368 34 1 2 377
28657 21 1 3 610
17711 13 8 5 987
10946 6765 4181 2584 1597

Answer 1

As juanchopanza pointed out, array indexing is from 0 to size - 1.
const int rowCount = 5, colCount = 5;
const int fibCount = rowCount * colCount - 1;
This would result in:
fibCount = 24 = ( 5 * 5 ) - 1;
Further down, at your while loop:
int R = 0, C = 0; //R for row, C for column
f = fibCount;
while (f >= 0) {
grid[R][C] = fibArr[f]; // f = 24; size = 24;
...
}
Here you take a value from your array fibArray with the index of 24. Last index would be 23.
Change this to:
const int fibCount = rowCount * colCount;
Then before your while loop:
f = fibCount - 1;
Besides that I would use a single dimensional array like this:
int rows = 5, cols = 5;
char* tst = new char[ rows * cols ];
int select_row = 2;
int select_col = 3;
tst[ select_row * cols + select_col ] = 65;
char c = tst[ select_row * cols + select_col ];
delete[] tst;