hdu 1002大数相加

</pre><p><pre name="code" class="cpp">#include<stdio.h>
#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
string add(string st1,string st2)
{
    if(st1.size()<st2.size())           //判断哪个长
    {
        string stemp=st1;
        st1=st2;
        st2=stemp;
    }
    reverse(st1.begin(),st1.end());         //将string类st1,st2逆转顺序
    reverse(st2.begin(),st2.end());
    int len1,len2;
    len1=st1.length();                      //计算各自的长度
    len2=st2.length();
    int in=0,num;                           //进位in初始化为0
    for(int i=0; i<len2; i++)
    {
        num=st1[i]-'0'+st2[i]-'0'+in;       //各位的和
        in=num/10;
        num%=10;
        st1[i]=num+'0';                     //放入较长的string里
    }
    for(int j=len2; j<len1; j++)            //如果遇到例如123 99892这样的样例,123处理完后需要向前边进位
    {
        num=st1[j]-'0'+in;
        in=num/10;
        num%=10;
        st1[j]=num+'0';
        //   cout<<in<<" "<<st1<<endl;
    }
    if(in==1)                               //相加的结果比原有的string都长
        st1+="1";
    reverse(st1.begin(),st1.end());
    return st1;
}
int main()
{
    string str1,str2;
    int t;
    cin>>t;
    int n=0;
    while(t--)
    {
        cin>>str1>>str2;
        if(n)
            cout<<endl;
        cout<<"Case "<<++n<<":";
        cout<<endl<<str1<<" + "<<str2<<" = ";
        cout<<add(str1,str2)<<endl;
    }
    return 0;
}