【題解】ZeroJudge b115: TOI2008 2. 大數運算

#include <iostream>
#include <cstring>
using namespace std;

string s;
char c;
int la, lb, a[100], b[100], res[100];

void mul(){
    memset(res, 0, sizeof(res));
    for (int i = 0; i < la; i++){
        for (int j = 0; j < lb; j++){
            res[i+j] += a[i]*b[j];
        }
    }
    for (int i = 0; i < 100; i++){
        res[i+1] += res[i]/10;
        res[i] %= 10;
    }
}
bool cmp(int x){
    for (int i = lb-1; i >= 0; i--){
        if (a[i+x] < b[i]) return 0;
        if (a[i+x] > b[i]) return 1;
    }
    return 1;
}
void mns(int x){
    for (int i = 0; i < lb; i++){
        a[i+x] -= b[i];
    }
}
void div(){
    memset(res, 0, sizeof(res));
    for (int i = la-lb; i >= 0; i--){
        int cnt = 0;
        while (cmp(i)){
            mns(i);
            cnt++;
        }
        res[i] = cnt;
    }
}
void print(){
    bool flag = false;
    for (int i = 99; i >= 0; i--){
        if (res[i] != 0) flag = true;
        if (flag) cout << res[i];
    }
    if (!flag) cout << 0;
    cout << "\n";
}

int main() {
    while (cin >> s){
        la = s.length();
        memset(a, 0, sizeof(a));
        for (int i = 0; i < la; i++){
            a[la-i-1] = s[i]-'0';
        }
        cin >> c;
        cin >> s;
        lb = s.length();
        memset(b, 0, sizeof(b));
        for (int i = 0; i < lb; i++){
            b[lb-i-1] = s[i]-'0';
        }
        if (c == '*') mul();
        else div();
        print();
    }
}