根据 Stirling 近似公式,可以发现即使50!在整数范围内也已经无法表示,实在是没思路了
2条回答 默认 最新
- _GX_ 2022-03-21 03:16关注
#include <iostream> #include <string> #include <iterator> #include <vector> class BigInt { public: BigInt(unsigned int n = 0) { if (n == 0) _data.push_back('0'); else { while (n) { _data.push_back(n % 10 + '0'); n /= 10; } } } BigInt(const std::string &s) : _data(s.rbegin(), s.rend()) {} BigInt &operator+=(const BigInt &other); BigInt &operator*=(const BigInt &other); BigInt operator+(const BigInt &other) const { BigInt t = *this; t += other; return t; } BigInt operator*(const BigInt &other) const { BigInt t = *this; t *= other; return t; } private: std::string _data; friend std::istream &operator>>(std::istream &is, BigInt &a); friend std::ostream &operator<<(std::ostream &os, const BigInt &a); }; BigInt &BigInt::operator+=(const BigInt &other) { int carry = 0; std::string::iterator itr1 = _data.begin(); std::string::const_iterator itr2 = other._data.begin(); while (itr1 != _data.end() && itr2 != other._data.end()) { int a = *itr1 - '0'; int b = *itr2 - '0'; int c = a + b + carry; carry = c / 10; c %= 10; *itr1 = c + '0'; ++itr1; ++itr2; } while (itr1 != _data.end()) { int a = *itr1 - '0' + carry; carry = a / 10; a %= 10; *itr1 = a + '0'; ++itr1; } while (itr2 != other._data.end()) { int a = *itr2 - '0' + carry; carry = a / 10; a %= 10; _data.push_back(a + '0'); ++itr2; } if (carry > 0) _data.push_back(carry + '0'); return *this; } BigInt &BigInt::operator*=(const BigInt &other) { BigInt r; for (std::size_t i = 0; i < other._data.size(); i++) { int x = other._data[i] - '0'; int carry = 0; BigInt t = *this; for (std::string::iterator itr = t._data.begin(); itr != t._data.end(); ++itr) { int y = *itr - '0'; int a = x * y + carry; *itr = a % 10 + '0'; carry = a / 10; } if (carry > 0) t._data.push_back(carry + '0'); if (i > 0) { std::string zeros(i, '0'); t._data.insert(t._data.begin(), zeros.begin(), zeros.end()); } r += t; } *this = r; return *this; } std::istream &operator>>(std::istream &is, BigInt &a) { std::string s; is >> s; a = s; return is; } std::ostream &operator<<(std::ostream &os, const BigInt &a) { std::copy(a._data.rbegin(), a._data.rend(), std::ostream_iterator<char>(os)); return os; } BigInt factorial(int n) { BigInt r = 1; for (int i = 1; i <= n; i++) r *= i; return r; } int main() { std::cout << "50! = " << factorial(50) << std::endl; std::cout << "100! = " << factorial(100) << std::endl; return 0; }
$ g++ -Wall main.cpp $ ./a.out 50! = 30414093201713378043612608166064768844377641568960512000000000000 100! = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
本回答被题主选为最佳回答 , 对您是否有帮助呢?解决 无用评论 打赏 举报
悬赏问题
- ¥15 下图接收小电路,谁知道原理
- ¥15 装 pytorch 的时候出了好多问题,遇到这种情况怎么处理?
- ¥20 IOS游览器某宝手机网页版自动立即购买JavaScript脚本
- ¥15 手机接入宽带网线,如何释放宽带全部速度
- ¥30 关于#r语言#的问题:如何对R语言中mfgarch包中构建的garch-midas模型进行样本内长期波动率预测和样本外长期波动率预测
- ¥15 ETLCloud 处理json多层级问题
- ¥15 matlab中使用gurobi时报错
- ¥15 这个主板怎么能扩出一两个sata口
- ¥15 不是,这到底错哪儿了😭
- ¥15 关于#matlab#的问题:在模糊控制器中选出线路信息,在simulink中根据线路信息生成速度时间目标曲线(初速度为20m/s,15秒后减为0的速度时间图像)我想问线路信息是什么