hdu 1212 Big Number

Big Number

Time Limit: ²⁰⁰⁰⁄₁₀₀₀ MS (Java/Others) Memory Limit: ⁶⁵⁵³⁶⁄₃₂₇₆₈ K (Java/Others) Total Submission(s): 3386 Accepted Submission(s): 2305

Problem Description As we know, Big Number is always troublesome. But it’s really important in our ACM. And today, your task is to write a program to calculate A mod B.

To make the problem easier, I promise that B will be smaller than 100000.

Is it too hard? No, I work it out in 10 minutes, and my program contains less than 25 lines.

Input The input contains several test cases. Each test case consists of two positive integers A and B. The length of A will not exceed 1000, and B will be smaller than 100000. Process to the end of file.

Output For each test case, you have to ouput the result of A mod B.

Sample Input 2 3 12 7 152455856554521 3250

Sample Output 2 5 1521

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
using namespace std;
char a[1000+10]; int b;
int main(void){
#ifndef ONLINE_JUDGE
  freopen("1212.in", "r", stdin);
#endif
  while (~scanf("%s%d", a, &b)){
    int len = strlen(a); int x = a[len-1]-'0', po = 1;
    x = x % b; int y;
    for (int i = len - 2; i >= 0; --i){
      y = a[i] - '0'; po = (po * 10) % b;
      x = (x + y*po) % b;
    }
    printf("%d\n", x);
  }
  return 0;
}

看了讨论版学会的，不过还是有一点儿小问题，学一下数论吧……