把所有正整数排成三角形，第一行是 $1$，第二行是 $2,3$，第三行是 $4,5,6$，以此类推。那么第二种操作就是往右下移一格。
把操作反过来考虑，容易发现当 $y>x$ 时， 不断把 $y$ 往左上移一定是更优的（如果 $y$ 在第一列就先加 $1$）。
时间复杂度 $O(1)$。
QOJ.ac
QOJ
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Discussion #159 for Problem #6744. Square
Type: Editorial
Status: Open
Posted by: jiangly
Posted at: 2025-12-12 23:42:55
Last updated: 2025-12-12 23:42:59
题解
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