View Compilation Error

0_0_24535573_27267.cpp: In function 'int main()':
0_0_24535573_27267.cpp:14:22: error: 'strlen' was not declared in this scope
   int len1 = strlen(a) - 1, k = 0;
                      ^
0_0_24535573_27267.cpp:18:17: error: 'k' was not declared in this scope
    int temp = c[k] + a[len1--] + b[len2--] - 2 * '0';
                 ^
0_0_24535573_27267.cpp:30:6: error: 'k' was not declared in this scope
    c[k] += a[len1--] - '0',k++;
      ^
0_0_24535573_27267.cpp:32:6: error: 'k' was not declared in this scope
    c[k] += b[len2--] - '0',k++;
      ^
0_0_24535573_27267.cpp:33:9: error: 'k' was not declared in this scope
   if (c[k] > 0) k++;
         ^
0_0_24535573_27267.cpp:36:16: error: 'k' was not declared in this scope
   for (int i = k-1; i >=0; i--)
                ^