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下面给出的是大整数加, 减, 乘, 除int型的模板:
约定: 下面的模板实现中a, b均为HEX进制数, 且a[0]为a的最高位
const int HEX = 1e9;//运算采取的进制
deque<int> operator + (const deque<int> &a, const int b){//a,b均为HEX进制数,且a[0]为a的最高位
deque<int> res;
int carry = 0;//进位值
for(int i = a.size() - 1, tmp; i >= 0; --i)
tmp = a[i] + (i == 0) * b + carry, res.push_front(tmp % HEX), carry = tmp / HEX;
return carry? res.push_front(1), res: res;
}
deque<int> operator - (const deque<int> &a, const int b){//返回a - b,要求a >= b
deque<int> res;
for(int i = a.size() - 1, rent = 0, tmp; i >= 0; --i)//rent:借位标志
tmp = a[i] - (i == 0) * b - rent, res.push_back(tmp < 0? tmp + HEX: tmp), rent = (tmp < 0? 1: 0);
while(res.size() > 1 && !res[0]) res.pop_front();//去除高位多余0
return res;
}
deque<int> operator * (const deque<int> &a, const int b){//返回a * b
deque<int> res;
int carry = 0;
for(long long i = a.size() - 1, tmp; i >= 0; --i)
tmp = (long long)a[i] * b + carry, res.push_front(tmp % HEX), carry = tmp / HEX;
if(carry) res.push_front(carry);
while(res.size() > 1 && !res[0]) res.pop_front();//去除高位多余0
return res;
}
deque<int> operator / (const deque<int> &a, const int b){//返回a / b
deque<int> res;
for(long long i = 0, rem = 0, tmp; i < a.size(); ++i)
tmp = rem * HEX + a[i], res.push_back(tmp / b), rem = tmp % b;
while(res.size() > 1 && !res[0]) res.pop_front();
return res;
}
void show(const deque<int> &a){//打印num对应的整数值
printf("%d", a[0]);
for(int i = 1; i < a.size(); ++i) printf("%09d", a[i]);
}
下面的测试程序充分展示了上述模板的使用方法:
//大整数加,减,乘,除1位数(基于deque)
#include <cstdio>
#include <deque>
using namespace std;
const int HEX = 1e9;//运算采取的进制
deque<int> operator + (const deque<int> &a, const int b){//a,b均为HEX进制数,且a[0]为a的最高位
deque<int> res;
int carry = 0;//进位值
for(int i = a.size() - 1, tmp; i >= 0; --i)
tmp = a[i] + (i == 0) * b + carry, res.push_front(tmp % HEX), carry = tmp / HEX;
return carry? res.push_front(1), res: res;
}
deque<int> operator - (const deque<int> &a, const int b){//返回a - b,要求a >= b
deque<int> res;
for(int i = a.size() - 1, rent = 0, tmp; i >= 0; --i)//rent:借位标志
tmp = a[i] - (i == 0) * b - rent, res.push_back(tmp < 0? tmp + HEX: tmp), rent = (tmp < 0? 1: 0);
while(res.size() > 1 && !res[0]) res.pop_front();//去除高位多余0
return res;
}
deque<int> operator * (const deque<int> &a, const int b){//返回a * b
deque<int> res;
int carry = 0;
for(long long i = a.size() - 1, tmp; i >= 0; --i)
tmp = (long long)a[i] * b + carry, res.push_front(tmp % HEX), carry = tmp / HEX;
if(carry) res.push_front(carry);
while(res.size() > 1 && !res[0]) res.pop_front();//去除高位多余0
return res;
}
deque<int> operator / (const deque<int> &a, const int b){//返回a / b
deque<int> res;
for(long long i = 0, rem = 0, tmp; i < a.size(); ++i)
tmp = rem * HEX + a[i], res.push_back(tmp / b), rem = tmp % b;
while(res.size() > 1 && !res[0]) res.pop_front();
return res;
}
void show(const deque<int> &a){//打印num对应的整数值
printf("%d", a[0]);
for(int i = 1; i < a.size(); ++i) printf("%09d", a[i]);
}
int main(){
deque<int> a(1, 1);
for(int i = 1; i <= 20; ++i) a = a * i;
printf("Test case 1: a = "), show(a), printf("\n");
for(int i = 1; i <= 20; ++i) a = a / i;
printf("Test case 2: a = "), show(a), printf("\n");
printf("Test case 3: a = "), show(a - 1), printf("\n");
printf("Test case 4: a = "), show(a + 99999999), printf("\n");
return 0;
}
测试程序运行结果截图: