Problem A+B(Big Integer)

/*========================================================================
Problem A+B(Big Integer)
Time Limit:1000MS Memory Limit:65536KB
Total Submit:3205 Accepted:922
Description 
Give two positive integer A and B,calucate A+B.
Notice that A,B is no more than 500 digits.
Input 
The test case contain several lines.Each line contains two positive integer A and B.
Output 
For each input line,output a line contain A+B
Sample Input 
2 3
1231231231823192 123123123123123
1000000000000000 1
Sample Output 
5
1354354354946315
1000000000000001
Source
EOJ
==========================================================================*/

http://202.120.80.191/problem.php?problemid=1001

#include<stdio.h>
#include<string.h>
void sum(char a[],char b[],char c[]);//c=a+b
void swap(char a[]);
int main()
{
    char a[503],b[503],c[505];
    freopen("5.in","r",stdin);
    while(scanf("%s%s",a,b)!=EOF)//while(cin>>a>>b)
    {
        sum(a,b,c);
        printf("%s\n",c);
    }
    return 0;
}
void sum(char a[],char b[],char c[])//c=a+b
{
    int i,lenA,lenB,min,max;
    int carry=0,t;
    lenA=strlen(a);
    lenB=strlen(b);
    swap(a);
    swap(b);
    if(lenA>lenB)
    {
        max=lenA;
        min=lenB;
    }
    else
    {
        max=lenB;
        min=lenA;
    }
    for(i=0;i<min;i++)
    {
        t=(a[i]-'0')+(b[i]-'0')+carry;
        c[i]=t%10+'0';
        carry=t/10;
    }
    if(lenA>lenB)
    {
        for(i=min;i<max;i++)
        {
            t=(a[i]-'0')+carry;
            c[i]=t%10+'0';
            carry=t/10;
        }
    }
    else
    {
        for(i=min;i<max;i++)
        {
            t=(b[i]-'0')+carry;
            c[i]=t%10+'0';
            carry=t/10;
        }
    }
    if(carry!=0)
    {
        c[i]=carry+'0';
        i++;
    }
    c[i]='\0';
    swap(c);
}
void swap(char a[])
{
    int i,len=strlen(a),t=len/2;
    char ch;
    for(i=0;i<t;i++)
    {
        ch=a[i];
        a[i]=a[len-1-i];
        a[len-1-i]=ch;
    }
}