高精度计算模板

(我之前写了些什么玩意儿.)

一个结构体封装的高精度

#include<bits/stdc++.h>
using namespace std;
const int MOD = 10000;
struct bint{
  int a[5000], len;
  int& operator [] (int x) { return a[x]; }
  bint():len(1){ memset(a, 0, sizeof(a));}
  bint(long long x) { memset(a, 0, sizeof(a)); len = 0; while(x) { a[++len] = x % MOD; x /= MOD; } }
  void print(){
    printf("%d", a[len]);
    for (int i = len - 1; i > 0; i--)
      printf("%04d", a[i]);
  }
};
bint operator +(bint& a,bint& b){
  bint c;
  c.len = max(a.len, b.len);
  int x = 0;
  for (int i = 1; i <= c.len; i++){
      c[i] = a[i] + b[i] + x;
      x = c[i] / MOD;
        c[i] %= MOD;
  }
  if(x > 0)
    c[++c.len] = x;
  return c;
}
bint operator - (bint& a,bint& b){
  for (int i = 1; i <= b.len; i++)
      if(a[i] < b[i]){
          a[i] += MOD,a[i + 1]--;
          a[i] -= b[i];
      }   
}
bint operator * (bint& a,int b){
  int x = 0;
  for (int i = 1; i <= a.len; i++) 
    x += a[i] * b, a[i] = x % MOD, x /= MOD;
  if(x) a[++a.len] = x;
  return a;
}
bint operator *(bint& a, bint& b) {
  bint c;
  for(int i = 1; i <= a.len; i++) {
      int x = 0;
      for(int j = 1; j <= b.len; j++) 
          x += c[i + j - 1] + a[i] * b[j], c[i + j - 1] = x % MOD, x /= MOD;
      c[i + b.len] = x;
  }
  c.len = a.len + b.len;
  while(c.len > 1 && c[c.len] == 0) c.len--;
  return c;
}
bint operator / (bint& a,int b){
  bint c; c.len = a.len; int x = 0;
  for (int i = a.len; i > 0; i--) {
    x = x * MOD + a[i];
    c[i] = x / b;
    x %= b;
  }
  while(c[c.len] == 0 && c.len > 1) c.len--;
  return c;
}
bool operator < (bint& a,bint & b){
  if(a.len > b.len) return false;
  if(a.len < b.len) return true;
  for(int i = a.len; i >= 0; i--){
	if(a[i] < b[i]) return true;
	if(a[i] > b[i]) return false;
  }
  return false;
}