Quick and Easy Sprite –Victorian Rush Hour - Cocos2d-x by Example Beginner's Guide - page 213

The blocks we are currently using in the terrain will be stored inside a _blocks
vector.
We determine that the minimum width the _terrain object must have is 1.5
times the screen width. We'll keep adding blocks until the _terrain object
reaches this minimum width. We end by shuffling the patterns arrays and
adding the blocks.
2. The addBlocks method should look like this:
void Terrain::addBlocks(int currentWidth) {
while (currentWidth < _minTerrainWidth)
{
auto block = _blockPool.at(_blockPoolIndex);
_blockPoolIndex++;
if (_blockPoolIndex == _blockPool.size()) {
_blockPoolIndex = 0;
}
this->initBlock(block);
currentWidth += block->getWidth();
_blocks.pushBack(block);
}
this->distributeBlocks();
}
The logic inside the while loop will continue to add blocks until cur-
rentWidth of the _terrain object reaches _minTerrainWidth . Every
new block we retrieve from the pool in order to reach _minTerrainWidth
gets added to the _blocks vector.
3. Blocks are distributed based on their widths:
void Terrain::distributeBlocks() {
int count = (int) _blocks.size();
int i;
for (i = 0; i < count; i++) {
auto block = _blocks.at(i);
if (i != 0) {
auto prev_block = _blocks.at(i - 1);