洛谷 题解 P2312 【解方程】

Problem

P2312 【解方程】 >>>

record

• 用时： 1166ms
• 空间： 780KB(0.76MB)
• 代码长度： 2.95KB
• 提交记录： R9909587 >>>
• 注： 使用了
  1. o1 优化
  2. o2 优化
  3. o3 优化
  4. 快读快输 >>>

Solution

30 pts

枚举，使用 int，直接按题目所说暴力乱搞一通

Unaccepted 30
Ac:3
Wa:7

50 pts

∣a_i∣≤10^10000

所以高精度。

然而慢的一皮：

Unaccepted 50
Ac:5
Tle:5

评测记录 >>>

30 pts

考虑暴力优化。

考虑在模意义下进行暴力，可以减小误差。

注意：模的应该是质数，且应该多模数，防止误差。

质数应该多记住几个，考场上的时候很有用（如：哈希）

然后。。。就出锅了。

评测记录 >>>

Unaccepted 30
Ac:3
Wa:7

100 pts

请大家在NOIp上一定要：开 long long！

评测记录 >>>

Accepted 100
Ac:10

Code

// luogu-judger-enable-o2
/*** Problem: P2312 解方程. * Author:  航空信奥. * Date:    2018/08/19. * Upload:  Luogu. */
#pragma GCC optimize("O1")
#pragma GCC optimize("O2")
#pragma GCC optimize("O3")
#include <stdio.h>
#include <vector>
using namespace std;namespace hkxadpall {char BufferRead[1 << 15];int rLen = 0, rPos = 0;inline char Getchar(){if (rPos == rLen) rPos = 0, rLen = fread(BufferRead, 1, 1 << 15, stdin);if (rPos == rLen) return EOF;return BufferRead[rPos++];} template <typename _TpInt> inline _TpInt read();template <typename _TpInt> inline void write(_TpInt x);#   define Max_N 103
#   define Mod1  10007LL
#   define Mod2  19260817LL
#   define Mod3  100000007LLint n, m;long long a1[Max_N];long long a2[Max_N];long long a3[Max_N];bool isRight(long long *a, int x, long long mod){long long ans = a[n];for (int i = n - 1; i >= 0; i--) {ans = (ans * x + a[i]) % mod;}return (ans == 0);}int main() {   n = read<int>();m = read<int>();for (int i = 0; i <= n; i++) {bool flag = 0;char c = Getchar();while ((c > '9' || c < '0') && c != '-') c = Getchar();if (c == '-') flag = 1, c = Getchar();a1[i] = (c & 15);a2[i] = (c & 15);a3[i] = (c & 15);while ((c = Getchar()) <= '9' && c >= '0') {a1[i] = ((a1[i] * 10) + (c & 15)) % Mod1;a2[i] = ((a2[i] * 10) + (c & 15)) % Mod2;a3[i] = ((a3[i] * 10) + (c & 15)) % Mod3;}if (flag) {a1[i] = Mod1 - a1[i]; a2[i] = Mod2 - a2[i]; a3[i] = Mod3 - a3[i]; }}vector <int> answer;for (int i = 1; i <= m; i++) {if (isRight(a1, i, Mod1)&& isRight(a2, i, Mod2)&& isRight(a3, i, Mod3)) answer.push_back(i);}printf("%d\n", answer.size());for (int i = 0; i < answer.size(); i++)write(answer[i]), putchar(10);return 0;}template <typename _TpInt>inline _TpInt read()       {register int flag = 1;register char c = Getchar();while ((c > '9' || c < '0') && c != '-') c = Getchar();if (c == '-') flag = -1, c = Getchar();register _TpInt init = (c & 15);while ((c = Getchar()) <= '9' && c >= '0') init = (init << 3) + (init << 1) + (c & 15);return init * flag;}template <typename _TpInt>inline void write(_TpInt x){if (x < 0) {putchar('-');write<_TpInt>(~x + 1);}else {if (x > 9) write<_TpInt>(x / 10);   putchar(x % 10 + '0');}}
}int main()
{hkxadpall::main();return 0;
}