C++分离字符串中的数字和字符 转

#include <iostream>
#include <string>
#include <vector>
using namespace std;

void part(string _str, vector<int> &_num, vector<char> &_op)
{
    int sum = ;
    unsigned int i = ;

    while (i < _str.length())
    {
        if ('' <= _str.at(i) && _str.at(i) <= '')
            //还原连续的数字
            sum = sum *  + (_str.at(i) - '');
        else
        {
            _num.push_back(sum);
            _op.push_back(_str.at(i));
            sum = ;
        }
        i++;
    }

    //判断最后一个字符是否是数字
    if ( != sum)
        _num.push_back(sum);
}

int main()
{
    vector<int> num();
    vector<char> op();
    string str;

    cin >> str;
    part(str, num, op);

    //输出测试
    for (unsigned int i = ; i < num.size(); i++)
        cout << num.at(i) << " ";
    cout << endl;
    for (unsigned int i = ; i < op.size(); i++)
        cout << op.at(i) << " ";

    return ;
}

输入：

1+6+1/4+5*3

输出：

1 6 1 4 5 3
+ + / + *