Generate circle around certain point of a 2D matrix [closed] - c++

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I am trying to make a height map using randomly generated values in console using c++.
I have an array [50, 50] that is initialized as all 0s.
matrix = new int[rows * columns];
for (int i = 0; i < rows; i++) {
for (int k = 0; k < columns; k++) {
matrix[i * columns + k] = 0;
}
}
I use a loop to generate random points in the array and store the position of those points in a vector.
std::vector<int> sprinklePeaks(int peakDensity, int dimension) {
int count = 0;
std::vector<int> peaks;
for (int i = 0; i < peakDensity; i++) {
int peakIndex = randomize(0, dimension);
matrix[peakIndex] = randomize(69, 99);
peaks.push_back(peakIndex);
}
return peaks;
}
Problem: I am trying to generate a circle with a random radius around these points and fill the circle with randomly generated values, increasing as they approach the center, my circle generation seems to have the right coordinates for the center but the distance is wrong and no values get added to the matrix.
void circleGen(std::vector<int> peaks, int dimensions) {
for (int i = 0; i < peaks.size(); i++) {
int radius = randomize(5, 15);
int area = 3.14159 * radius * radius;
int index = peaks[i];
int x = index / 50;
int y = index % 50;
// std::cout << "Peak: " << peaks[i] << "\n";
// std::cout << "Peak Coordinates: [" << x << ", " << y << "]\n";
int peakHeight = matrix[peaks[i]];
for (int k = 0; k < radius * 2; k++) {
for (int j = 0; j < radius * 2; j++) {
int distance = sqrt((i - radius) * (i - radius) + (j - radius) * (j - radius));
matrix[x - j * columns + y - k] = randomize(10, 20);
}
}
}
}

Answer 1

First issue could be that you don't have bounds checking. I assume you should not change the matrix (and more importantly the surrounding memory) if coordinates are out of the bounds.
Second issue I see is that you calculate distance, but then you don't use this value.
Third issue could be that you want to add to the matrix cell, not replace the value. In line matrix[x - j * columns + y - k] = randomize(10, 20); maybe it should be += instead of =. And distance should participate in the right-side. Or you want to replace, but only if new value is greater than the existing value.
Fourth, as Andrej in the comments mentioned, the math to calculate the index in the matrix is wrong. Should use parentheses, (x - j) * columns + y - k