浙江工商大学23调剂（四舍五入）

题解：

#include <iostream>
#include <vector>
#include <queue>
#include <string>
#include <cmath>
#include <sstream>
using namespace std;

struct State {
    int int_part;
    vector<char> decimals;
};

double calculateValue(const State& s) {
    double val = s.int_part;
    double factor = 0.1;
    for (char c : s.decimals) {
        val += (c - '0') * factor;
        factor /= 10;
    }
    return val;
}

string formatOutput(double value) {
    ostringstream oss;
    if (value == floor(value)) {
        oss << static_cast<long long>(value);
    } else {
        oss << value;
        string s = oss.str();
        size_t dot_pos = s.find('.');
        if (dot_pos != string::npos) {
            size_t last_non_zero = s.find_last_not_of('0');
            if (last_non_zero == dot_pos) {
                s = s.substr(0, dot_pos);
            } else if (last_non_zero != string::npos) {
                s = s.substr(0, last_non_zero + 1);
            }
        }
        return s;
    }
    return oss.str();
}

int main() {
    string s;
    cin >> s;
    int int_part = 0;
    vector<char> decimals;
    size_t dot_pos = s.find('.');
    if (dot_pos != string::npos) {
        int_part = stoi(s.substr(0, dot_pos));
        string dec_part = s.substr(dot_pos + 1);
        for (char c : dec_part) {
            decimals.push_back(c);
        }
    } else {
        int_part = stoi(s);
    }

    double max_val = calculateValue({int_part, decimals});
    queue<State> q;
    q.push({int_part, decimals});

    while (!q.empty()) {
        State current = q.front();
        q.pop();
        int len = current.decimals.size();

        for (int i = 1; i <= len - 1; ++i) { // 检查第i+1位（索引i）
            if (current.decimals[i] < '5') continue;

            vector<char> new_decimals(current.decimals.begin(), current.decimals.begin() + i);
            int new_int = current.int_part;
            int carry = 1;

            // 处理进位
            for (int k = new_decimals.size() - 1; k >= 0; --k) {
                int digit = new_decimals[k] - '0';
                digit += carry;
                carry = digit / 10;
                new_decimals[k] = (digit % 10) + '0';
                if (carry == 0) break;
            }

            if (carry > 0) {
                new_int += carry;
                new_decimals.clear();
            }

            // 检查是否需要进一步进位到整数部分
            if (!new_decimals.empty()) {
                double decimal_val = 0.0;
                double factor = 0.1;
                for (char c : new_decimals) {
                    decimal_val += (c - '0') * factor;
                    factor /= 10;
                }
                if (decimal_val >= 0.5) {
                    new_int += 1;
                    new_decimals.clear();
                }
            }

            // 计算新值
            double new_value = new_int;
            if (!new_decimals.empty()) {
                new_value = calculateValue({new_int, new_decimals});
            }
            if (new_value > max_val) {
                max_val = new_value;
            }

            // 若仍有小数部分，继续处理
            if (!new_decimals.empty()) {
                q.push({new_int, new_decimals});
            }
        }
    }

    cout << formatOutput(max_val) << endl;
    return 0;
}