分块
建图
1.
int Size, Num, L[Maxsn + 5], R[Maxsn + 5], Block[Maxn + 5];
void Build (int l, int r) {
Size = sqrt (r - l + 1);
Num = ceil ((r - l + 1) * 1.0 / Size);
for (int i = 1; i < Num; i++) {
L[i] = 1 + (i - 1) * Size;
R[i] = i * Size;
for (int j = L[i]; j <= R[i]; j++)
Block[j] = i;
}
L[Num] = 1 + (Num - 1) * Size;
R[Num] = r;
for (int j = L[Num]; j <= R[Num]; j++)
Block[j] = Num;
}
2.
#define l(x) (((x) - 1) * Size + 1)
#define r(x) (Min ((x) * Size, n))
#define Get(x) (((x) - 1) / Size + 1)