LuoGu: CF797E Array Queries
CF: E. Array Queries
对于所有 $k \le \sqrt n$ ，可以 $O(n \sqrt n)$ 预处理；对于 $k > \sqrt n$ ，暴力算，复杂度 $O(\sqrt n)$ 。
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| #include <cstdio>
#include <cmath>
using namespace std;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
flag && (x = ~x + 1);
}
template <class Type>
void write(Type x)
{
x < 0 && (putchar('-'), x = ~x + 1);
x > 9 && (write(x / 10), 0);
putchar(x % 10 + '0');
}
const int N = 1e5 + 10, M = 320;
int n, m, b, w[N], f[N][M];
int dfs (int p, int k)
{
if (p > n)
return 0;
if (k <= b && f[p][k])
return f[p][k];
int t = dfs(p + w[p] + k, k) + 1;
k <= b && (f[p][k] = t);
return t;
}
int main ()
{
read(n);
for (int i = 1; i <= n; i++)
read(w[i]);
b = sqrt(n);
read(m);
for (int p, k; m; m--)
{
read(p), read(k);
write(dfs(p, k)), puts("");
}
return 0;
}
|