朴素高精度四则运算模板

不考虑负数情况。还包含了高精度和 int 类型的乘除运算。

#include <stdio.h>
#include <string.h>
#include <algorithm>

using namespace std;

struct bign {
    int v[1218];
    int len;
    
    bign() { memset(v, 0, sizeof v), len = 0; }
    
    void _load(char *num, int beg, int end)
    {
        int i, cnt = 0;
        len = end-beg+1;
        for (i = end; i >= beg; --i) v[++cnt] = num[i]-'0';
        return ;
    }
    
    void _print()
    {
        for (int i = len; i >= 1; --i) putchar(v[i]+'0');
        return ;
    }
    
};

bool operator < (bign a, bign b)
{
    if (a.len != b.len) return a.len < b.len;
    for (int i = a.len; i >= 1; --i)
        if (a.v[i] != b.v[i]) return a.v[i] < b.v[i];
    return false;
}

bool operator == (bign a, bign b)
{
    if (a.len != b.len) return false;
    for (int i = 1; i <= a.len; ++i)
        if (a.v[i] != b.v[i]) return false;
    return true;
}

bool operator <= (bign a, bign b) { return a < b || a == b; }

bign operator + (bign a, bign b)
{
    bign c; int i;
    c.len = max(a.len, b.len)+1;
    for (i = 1; i <= c.len; ++i)
        c.v[i] = a.v[i]+b.v[i];
    for (i = 1; i <= c.len; ++i)
        if (c.v[i] >= 10) c.v[i] %= 10, ++c.v[i+1];
    while (!c.v[c.len] && c.len > 1) --c.len;
    return c;
}

bign operator - (bign a, bign b)
{
    bign c; int i;
    c.len = a.len;
    for (i = 1; i <= c.len; ++i) c.v[i] = a.v[i]-b.v[i];
    for (i = 1; i <= c.len; ++i)
        if (c.v[i] < 0) c.v[i] += 10, --c.v[i+1];
    while (!c.v[c.len] && c.len > 1) --c.len;
    return c;
}

bign operator * (bign a, bign b)
{
    bign c;
    int i, j;
    c.len = a.len + b.len;
    for (i = 1; i <= a.len; ++i)
        for (j = 1; j <= b.len; ++j)
            c.v[i+j-1] += a.v[i]*b.v[j];
    for (i = 1; i <= c.len; ++i)
        if (c.v[i] >= 10) c.v[i+1] += c.v[i]/10, c.v[i] %= 10;
    while (!c.v[c.len] && c.len > 1) --c.len;
    return c;
}

bign operator / (bign a, bign b)
{
    if (a < b) return a;
    int t = a.len-b.len, i; bign tmp, c;
    for (i = 1; i <= b.len; ++i) tmp.v[t+i] = b.v[i];
    tmp.len = t+b.len, c.len = t+1;
    for (i = 0; i < c.len; ++i) {
        while (tmp < a) a = a-tmp, ++c.v[c.len-i];
        for (int j = 1; j < tmp.len; ++j) tmp.v[j] = tmp.v[j+1];
        tmp.v[tmp.len--] = 0;
    }
    while (!c.v[c.len] && c.len > 1) --c.len;
    //余数为a
    return c;
}

bign _mul(bign a, int b)
{
    bign c; int i, d = 0;
    c.len = a.len;
    for (i = 1; i <= c.len; ++i)
        c.v[i] = a.v[i]*b+d, d = c.v[i]/10, c.v[i] %= 10;
    while (d) c.v[++c.len] = d%10, d /= 10;
    while (!c.v[c.len] && c.len > 1) --c.len;
    return c;
}

bign _div(bign a, int b)
{
    bign c; int i, d = 0;
    c.len = a.len;
    for (i = c.len; i >= 1; --i)
        c.v[i] = (d*10+a.v[i])/b, d = (d*10+a.v[i])%b;
    while (!c.v[c.len] && c.len > 1) --c.len;
    //余数为d
    return c;
}

int main()
{
    bign a, b; char input[9000];
    scanf("%s", input), a._load(input, 0, strlen(input)-1);
    scanf("%s", input), b._load(input, 0, strlen(input)-1);
    (a+b)._print(), putchar('
');
    (a-b)._print(), putchar('
');
    (a*b)._print(), putchar('
');
    (a/b)._print(), putchar('
');
    return 0;
}