hoj 1533 Fibonacci Numbers

http://acm.hit.edu.cn/hoj/problem/view?id=1533

用字符串表示整数，进行大数加法运算

/*This Code is Submitted by billforum for Problem 1533 at 2012-03-30 14:50:02*/
#include <iostream>
 #include <string.h>
 #include <stdio.h>
 #include <stack>
 using namespace std;
 
 
 int main()
 {
    string t1,t2,t;
        int z;
         int num;
        while(scanf("%d",&num)!=EOF)
        {
                if(num==1||num==2)
                {
                        printf("1\n");
                }
                else
                {
                        t1="1";
                        t2="1";
                        for(int k=3;k<=num;k++)
                        {
                                int i,j;
                                z=0;
                                t="";
                                for(i=t1.length()-1,j=t2.length()-1;i>=0;i--,j--)
                                {
                                        t+=(char)((t1[i]-48+t2[j]-48+z)%10+48);
                                        z=(t1[i]-48+t2[j]-48+z)/10;
                                }
                                for(i=j;i>=0;i--)
                                {
                                        t+=(char)((t2[i]-48+z)%10+48);
                                        z=(t2[j]-48+z)/10;
                                }
                                if(z>0)
                                {
                                        t+=(char)(z+48);
                                }
                                t1="";
                                t1=t2;
                                t2="";
                                for(int ii=t.length()-1;ii>=0;ii--)
                                        t2+=t[ii];
                        }
                        cout<<t2<<endl;
                }
        }
         return 0;
 }