请检查操作一的合并。

如果您是这样写的：

if (opt == 'M') {
	cin >> x >> y;
	if (tr[x] || tr[y] || x == y)continue;
	x = find(x), y = find(y);
	rt[x] = rt[y] = merge(x, y);
}

请改成：

if (opt == 'M') {
	cin >> x >> y;
	if (tr[x] || tr[y])continue;
	x = find(x), y = find(y);
	if (x != y)rt[x] = rt[y] = merge(x, y);
}

具体原因不明。