dropdown.cpp

// 消除后对应空位由上方元素填充
void dropdown()
{
	vector<pair<int, int>> points;
	for(int k = 0; k < n; k++)  // 蛮力扫描所有列，效率待提高
    {       
        int count = 0;
        // 检查该列是否需要填充
        for(int curi = m-1; curi >= 0; curi--)
        {
            if(ar[curi][k] == 0)
            {
                int ci = curi - 1;
				        int ni = curi;
                // 计算该列被消除的个数
                while(ci >= 0 && ar[ci][k] == 0)
                {
                    count++;
					          ci--;
                }
                ci = curi - count - 1;
                // 元素下落
                while(ci >= 0)
                {
                    ar[ni][k] = ar[ci][k];
                    points.push_back(make_pair(ni, k));
                    ni--;
                    ar[ci--][k] = 0;
                }
            }
            
        }
    }
	//cout << "After dropdown" << endl;
	//print_array();


	// 检查下落后是否还有可消除元素
	// 对受下落影响的元素进行扫描
	bool can_eliminate = false;
	for (int ii = 0; ii < points.size(); ii++)
		if (eliminate(points[ii].first, points[ii].second))
			can_eliminate = true;
	if (can_eliminate)
		dropdown();	
}