蓝桥杯B15-4,R格式

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
int main() {
    vector<char>v;
    int n,tag;
    string d;
    cin >> n >> d;
    for (int i = d.size() - 1; i >= 0;i--) {
        if (d[i] != '.') {
            v.push_back(d[i]-'0');
        }
        else {
            tag = i;
        }
    }
    tag = d.length() - tag - 1;
    for (int i = 0; i < n;i++) {
        int tmp = 0;
        for (int j = 0; j < v.size();j++) {
            v[j] *= 2;
            v[j] += tmp;
            tmp = v[j] / 10;
            v[j] %= 10;
        }
        if (tmp) {
            v.push_back(tmp);
        }
    } 
    if (v[tag - 1] >= 5) {
        v[tag] += 1;
    }
    for (int i = v.size() - 1; i >= tag; i--) {
        cout << int(v[i]);
    }
    return 0;
}