C++大数相加

c++

tring sum(string s1,string s2)
{
    if(s1.length()<s2.length())
    {
        string temp=s1;
        s1=s2;
        s2=temp;
    }
    int i,j;
    for(i=s1.length()-1,j=s2.length()-1;i>=0;i--,j--)
    {
        s1[i]=char(s1[i]+(j>=0?s2[j]-‘0‘:0));
        if(s1[i]-‘0‘>=10)
        {
            s1[i]=char((s1[i]-‘0‘)%10+‘0‘);
            if(i) s1[i-1]++;
            else s1=‘1‘+s1;
        }
    }
    return s1;
}

C语言

char s1[1000];
char s2[1000];
void Add1()
 {
     int num1[2000],num2[20000];
     memset(num1,0,sizeof(num1));
     memset(num2,0,sizeof(num2));
     int i,j;
     int len1=strlen(s1);
     int len2=strlen(s2);
     for(i=len1-1,j=0;i>=0;i--)
             num1[j++]=s1[i]-‘0‘;
     for(i=len2-1,j=0;i>=0;i--)
             num2[j++]=s2[i]-‘0‘;
     for(i=0;i<2000;i++)
     {
         num1[i]+=num2[i];
         if(num1[i]>9)
         {
             num1[i]-=10;
             num1[i+1]++;
         }
     }
    for( i=1999;i>=0;i--)
        if(num1[i]!=0)
            break;
    if(i==-1)
        printf("0",num1[i]);
    for(;i>=0;i--)
                printf("%d",num1[i]);
    printf("\n");

 }