实现string到unsigned int的转换

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

//实现string到unsigned int的转换
unsigned int string_to_unsigned_int(string str)
{
	unsigned int result(0);//最大可表示值为4294967296（=2‘32-1）
	//从字符串首位读取到末位（下标由0到str.size() - 1）
	for (int i = str.size()-1;i >= 0;i--)
	{
		unsigned int temp(0),k = str.size() - i - 1;
		//判断是否为数字
		if (isdigit(str[i]))
		{
			//求出数字与零相对位置
			temp = str[i] - "0";
			while (k--)
				temp *= 10;
			result += temp;
		}
		else
			//exit(-1);
			break;
	}
	return result;
}

int main()
{
	string str;
	while (cin >> str)
	{
		cout << "the result is: " << string_to_unsigned_int(str) << endl;
	}
	return 0;
}