大数相加

string bigIntegerAdd(string s1, string s2)
{
int len1 = s1.size();
int len2 = s2.size();
int len = len1 > len2 ? len1+1 : len2+1;
string res(len, '0');

int i, j, k;
int carry = 0, sum;
for (i = len1-1, j = len2-1, k = len-1; i >= 0 || j >= 0; i--, j--, k--)
{
sum = carry;
if (i >= 0)
sum += s1[i] - '0';
if (j >= 0)
sum += s2[j] - '0';
if (sum >= 10)
{
res[k] += sum - 10;
carry = 1;
}
else
{
res[k] += sum;
carry = 0;
}
}
if (carry == 1)
{
res[k] = '1';
return res;
}
else
return res.substr(1);
}

C语言实现高精度大整数的加法