# C++高精度，加减乘除取余，但错了，帮看看哪里错了，带错误数据

0

``````class BigInt{
public:
#define Value(x, nega) ((nega) ? -(x) : (x))
#define At(vec, index) ((index) < vec.size() ? vec[(index)] : 0)
static int absComp(const BigInt &lhs, const BigInt &rhs)
{
if (lhs.size() != rhs.size())
return lhs.size() < rhs.size() ? -1 : 1;
for (int i = lhs.size() - 1; i >= 0; --i)
if (lhs[i] != rhs[i])
return lhs[i] < rhs[i] ? -1 : 1;
return 0;
}
using Long = long long;
const static int Exp = 9;
const static Long Mod = 1000000000;
mutable std::vector<Long> val;
mutable bool nega = false;
void trim() const
{
while (val.size() && val.back() == 0)
val.pop_back();
if (val.empty())
nega = false;
}
int size() const { return val.size(); }
Long &operator[](int index) const { return val[index]; }
Long &back() const { return val.back(); }
BigInt(int size, bool nega) : val(size), nega(nega) {}
BigInt(const std::vector<Long> &val, bool nega) : val(val), nega(nega) {}

friend std::ostream &operator<<(std::ostream &os, const BigInt &n)
{
if (n.size())
{
if (n.nega)
putchar('-');
for (int i = n.size() - 1; i >= 0; --i)
{
if (i == n.size() - 1)
printf("%lld", n[i]);
else
printf("%0*lld", n.Exp, n[i]);
}
}
else
putchar('0');
return os;
}
friend BigInt operator+(const BigInt &lhs, const BigInt &rhs)
{
BigInt ret(lhs);
return ret += rhs;
}
friend BigInt operator-(const BigInt &lhs, const BigInt &rhs)
{
BigInt ret(lhs);
return ret -= rhs;
}
BigInt(Long x = 0)
{
if (x < 0)
x = -x, nega = true;
while (x >= Mod)
val.push_back(x % Mod), x /= Mod;
if (x)
val.push_back(x);
}
BigInt(const char *s)
{
int bound = 0, pos;
if (s[0] == '-')
nega = true, bound = 1;
Long cur = 0, pow = 1;
for (pos = strlen(s) - 1; pos >= Exp + bound - 1; pos -= Exp, val.push_back(cur), cur = 0, pow = 1)
for (int i = pos; i > pos - Exp; --i)
cur += (s[i] - '0') * pow, pow *= 10;
for (cur = 0, pow = 1; pos >= bound; --pos)
cur += (s[pos] - '0') * pow, pow *= 10;
if (cur)
val.push_back(cur);
}
BigInt &operator+=(const BigInt &rhs)
{
const int cap = std::max(size(), rhs.size()) + 1;
val.resize(cap);
int carry = 0;
for (int i = 0; i < cap - 1; ++i)
{
val[i] = Value(val[i], nega) + Value(At(rhs, i), rhs.nega) + carry, carry = 0;
if (val[i] >= Mod)
val[i] -= Mod, carry = 1;
else if (val[i] < 0)
val[i] += Mod, carry = -1;
}
if ((val.back() = carry) == -1)
{
nega = true, val.pop_back();
bool tailZero = true;
for (int i = 0; i < cap - 1; ++i)
{
if (tailZero && val[i])
val[i] = Mod - val[i], tailZero = false;
else
val[i] = Mod - 1 - val[i];
}
}
trim();
return *this;
}
friend BigInt operator-(const BigInt &rhs)
{
BigInt ret(rhs);
ret.nega ^= 1;
return ret;
}
BigInt &operator-=(const BigInt &rhs)
{
rhs.nega ^= 1;
*this += rhs;
rhs.nega ^= 1;
return *this;
}
friend BigInt operator*(const BigInt &lhs, const BigInt &rhs)
{
const int cap = lhs.size() + rhs.size() + 1;
BigInt ret(cap, lhs.nega ^ rhs.nega);
//j < l.size(),i - j < rhs.size() => i - rhs.size() + 1 <= j
for (int i = 0; i < cap - 1; ++i) // assert(0 <= ret[cap-1] < Mod)
for (int j = std::max(i - rhs.size() + 1, 0), up = std::min(i + 1, lhs.size()); j < up; ++j)
{
ret[i] += lhs[j] * rhs[i - j];
ret[i + 1] += ret[i] / Mod, ret[i] %= Mod;
}
ret.trim();
return ret;
}
BigInt &operator*=(const BigInt &rhs) { return *this = *this * rhs; }
friend BigInt operator/(const BigInt &lhs, const BigInt &rhs)
{
static std::vector<BigInt> powTwo{BigInt(1)};
static std::vector<BigInt> estimate;
estimate.clear();
if (absComp(lhs, rhs) < 0)
return BigInt();
BigInt cur = rhs;
int cmp;
while ((cmp = absComp(cur, lhs)) <= 0)
{
estimate.push_back(cur), cur += cur;
if (estimate.size() >= powTwo.size())
powTwo.push_back(powTwo.back() + powTwo.back());
}
if (cmp == 0)
return BigInt(powTwo.back().val, lhs.nega ^ rhs.nega);
BigInt ret = powTwo[estimate.size() - 1];
cur = estimate[estimate.size() - 1];
for (int i = estimate.size() - 1; i >= 0 && cmp != 0; --i)
if ((cmp = absComp(cur + estimate[i], lhs)) <= 0)
cur += estimate[i], ret += powTwo[i];
ret.nega = lhs.nega ^ rhs.nega;
return ret;
}
bool operator==(const BigInt &rhs) const
{
return nega == rhs.nega && val == rhs.val;
}
bool operator!=(const BigInt &rhs) const { return nega != rhs.nega || val != rhs.val; }
bool operator>=(const BigInt &rhs) const { return !(*this < rhs); }
bool operator>(const BigInt &rhs) const { return !(*this <= rhs); }
bool operator<=(const BigInt &rhs) const
{
if (nega && !rhs.nega)
return true;
if (!nega && rhs.nega)
return false;
int cmp = absComp(*this, rhs);
return nega ? cmp >= 0 : cmp <= 0;
}
bool operator<(const BigInt &rhs) const
{
if (nega && !rhs.nega)
return true;
if (!nega && rhs.nega)
return false;
return (absComp(*this, rhs) < 0) ^ nega;
}
friend BigInt operator%(const BigInt &a, const BigInt &b) {
return a - (a / b) * b;
}
BigInt operator%=(const BigInt &b) {
return *this = *this % b;
}
void swap(const BigInt &rhs) const
{
std::swap(val, rhs.val);
std::swap(nega, rhs.nega);
}
};
``````

### input:

``````393908905943805939049136388151512092795248751812850407919644368889770680461420583
96681286331322928654007712583130933920474979370998589
``````

### output:

``````393908905943805939049136388248193379126571680466858120502775302810245659832419172
393908905943805939049136388054830806463925823158842695336513434969295701090421994
38083619724011254261905972927864946941840717899746492944683233630255056851602290529419753377726732358591557722636179431849662228557387
4074303527508888970400505616
50939107156270655711552235183567119436538268038844759
``````

### my output:

``````39390890594380593949136388248193379126571680466858120502775302810245659832419172
393908905943805939491363885483080646392582315884269533651343496929570190421994
38083619724011254261905972927864946941840717899746492944683233630255056851602290529419753377726732358591557722636179431849662228557387
474303527508888970400505616
5093910715627065571155223518356711943653826838844759
``````
dingcongyu | 初学一级 | 园豆：188

-1

`C++`高精度一般都是字符串数字运算，因为字符串没有长度的限制，比如 `1.12345678910987654321 + 2.9876543210987654321`，如果你使用基本数据类型 `double`，那么你只能保留小数点后6位的精度，6位之后的数据精度就丢失了，如果我们使用字符串去加减乘除，我们不管小数点后有多少位，我们都能保证计算的过程中不会造成精度丢失的情况。

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