Implementing Midpoint Displacement - c++

Question

I have been able to successfully implement midpoint displacement in a numbered array in another program and so i'v tried to implement it in a 3D world to create terrain however the outcome of the algorithm isn't what i expected.
void MidPointDisplacement(float grid[][WIDTH], int left, int right, int top, int bottom, int row, int col)
{
int centreX = (left + right) / 2; //Get the centre of the row
int centreY = (top + bottom) / 2; //Get the centre of the column
if (centreX == left)
{
return;
}
if (centreY == bottom)
{
return;
}
grid[top][centreX] = ((grid[top][left] + grid[top][right]) / 2) + jitter; //define top
grid[bottom][centreX] = ((grid[bottom][left] + grid[bottom][right]) / 2) + jitter; //define bottom
grid[centreY][left] = ((grid[top][left] + grid[bottom][left]) / 2) + jitter; //define left
grid[centreY][right] = ((grid[top][right] + grid[bottom][right]) / 2) + jitter; //define right
grid[centreX][centreY] = ((grid[centreY][left] + grid[centreY][right] + grid[top][centreX] + grid[bottom][centreX]) / 4) + jitter; //Get centre
//decreased the random values
RANDMAX / 2;
RANDMIN / 2;
MidPointDisplacement(grid, centreX, right, centreY, bottom, row, col);
MidPointDisplacement(grid, left, centreX, top, centreY, row, col);
MidPointDisplacement(grid, centreX, right, top, centreY, row, col);
MidPointDisplacement(grid, left, centreX, centreY, bottom, row, col);
}
The result of the above is this:
3D Midpoint Displacement
However I expected a terrain like this:
What I expected
Is there any reason why this maybe? I initially thought it could've been the jitter however decreasing the initial value doesn't solve this problem.
float jitter = rand() % (int)(RANDMAX - RANDMIN + 1) + RANDMIN;
Jitter is a global float that takes a random value between RANDMAX (initial value of 5.0f) and RANDMIN (initial value of -5.0f).
Solution:
To fix the above error I deleted the jitter I had created in the program and instead made jitter a float variable of 1.
In the MidpointDisplacement function I changed this:
grid[top][centreX] = ((grid[top][left] + grid[top][right]) / 2) + jitter; //define top
grid[bottom][centreX] = ((grid[bottom][left] + grid[bottom][right]) / 2) + jitter; //define bottom
grid[centreY][left] = ((grid[top][left] + grid[bottom][left]) / 2) + jitter; //define left
grid[centreY][right] = ((grid[top][right] + grid[bottom][right]) / 2) + jitter; //define right
grid[centreX][centreY] = ((grid[centreY][left] + grid[centreY][right] + grid[top][centreX] + grid[bottom][centreX]) / 4) + jitter; //Get centre
To this:
grid[top][centreX] = ((grid[top][left] + grid[top][right]) / 2) + ((rand() % 256) - 128) / 128.0F * JITTER_RANGE * jitter; //define top
grid[bottom][centreX] = ((grid[bottom][left] + grid[bottom][right]) / 2) + ((rand() % 256) - 128) / 128.0F * JITTER_RANGE * jitter; //define bottom
grid[centreY][left] = ((grid[top][left] + grid[bottom][left]) / 2) + ((rand() % 256) - 128) / 128.0F * JITTER_RANGE * jitter; //define left
grid[centreY][right] = ((grid[top][right] + grid[bottom][right]) / 2) + ((rand() % 256) - 128) / 128.0F * JITTER_RANGE * jitter; //define right
grid[centreY][centreX] = ((grid[centreY][left] + grid[centreY][right] + grid[top][centreX] + grid[bottom][centreX]) / 4) + ((rand() % 256) - 128) / 128.0F * JITTER_RANGE * jitter; //Get centre
I then called the function again as done before however this time I divided the jitter by 2.
Also, I discovered that I stupidly had centreX and centreY the wrong way around in the line(Not changed here):
grid[centreX][centreY] = ((grid[centreY][left] + grid[centreY][right] + grid[top][centreX] + grid[bottom][centreX]) / 4) + jitter; //Get centre