View Compilation Error

0_0_20197154_5649.cpp: In function 'int main()':
0_0_20197154_5649.cpp:21:26: error: 'strlen' was not declared in this scope
    len[i] = strlen(str[i]);
                          ^
0_0_20197154_5649.cpp:24:29: error: 'memset' was not declared in this scope
   memset(num, 0, sizeof(num));
                             ^