替换字符串

给定一个字符串，请你将字符串重新编码，将连续的字符替换成“连续出现的个数+字符”。比如字符串AAAABCCDAA会被编码成4A1B2C1D2A。 

输入描述:

每个测试输入包含1个测试用例 每个测试用例输入只有一行字符串，字符串只包括大写英文字母，长度不超过10000。

#include <iostream>
#include <sstream>

using namespace std;

string IntToString(int number) {
    stringstream stream;
    stream << number;
    string res;
    stream >> res;
    return res;
}
string CalString(string& str) {
    if (str.size() == 0)
        return str;

    int start = 0;
    int end = 0;
    string res = "";
    string wordLen = "";

    for (int i = 0; i <= str.size(); i++) {
        if (str[start] != str[i]) {
            end = i;
            wordLen = IntToString(end - start);
            res += wordLen + str[start];
            start = i;
        }
    }

    return res;

}



int main()
{
    std::string input;

    std::getline(std::cin, input);
    std::string res = CalString(input);
    cout << res << endl;
}