原题: 

Calculate a + b
 
Input

The input will consist of a series of pairs of integers a and b,
separated by a space, one pair of integers per line. 

Output

For each pair of input integers a and b you should output the sum
 of a and b in one line,and with one line of utput for each line in input.

Sample Input
1 5

Sample Output
6

Hint
Use + operator

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


int main()
{
    string a,b;
    char *c = NULL;
    long a_len = 0,b_len = 0,c_len=0,min_len;
    int one_bit = 0;
    bool flag = false;
    while(cin>>a>>b)
    {
        if (a[0]!='-'&&b[0]!='-')
        {
            a_len = a.length();
            b_len = b.length();
            c_len = (a_len>b_len?a_len:b_len)+1;
            min_len = a_len<b_len?a_len:b_len;
            c = new char[c_len+1];
            c[c_len] = '\0';
            c[0] = 'A';
            while(min_len>0)
            {
                one_bit=int(a[a_len-1])+int(b[b_len-1])-96;
                if(flag)
                    one_bit++;
                if(one_bit>9)
                {
                    one_bit -= 10;
                    flag = true;
                }
                else
                    flag = false;
                c[c_len-1] = char(one_bit+48);
                one_bit = 0;
                c_len--;
                min_len--;
                a_len--;
                b_len--;
            }
            if(a_len==0)
            {
                while(b_len>0)
                {
                    one_bit=int(b[b_len-1])-48;
                    if(flag)
                        one_bit++;
                    if(one_bit>9)
                    {
                        one_bit -= 10;
                        flag = true;
                    }
                    else
                        flag = false;
                    c[c_len-1] = char(one_bit+48);
                    one_bit = 0;
                    c_len--;
                    b_len--;
                }
            }

            if(b_len==0)
            {
                while(a_len>0)
                {
                    one_bit=int(a[a_len-1])-48;
                    if(flag)
                        one_bit++;
                    if(one_bit>9)
                    {
                        one_bit -= 10;
                        flag = true;
                    }
                    else
                        flag = false;
                    c[c_len-1] = char(one_bit+48);
                    one_bit = 0;
                    c_len--;
                    a_len--;
                }
            }
            
            if(flag)
                c[0] = '1';
        }

        if (flag)
            cout<<c<<endl;
        else
            cout<<++c<<endl;
        flag = false;
        c = NULL;
    }
    

    return 0;
}

这是当时提交的源程序,本以为要考虑负数的,原来不用......