View Compilation Error

0_0_17632777_31626.cpp: In function 'int main()':
0_0_17632777_31626.cpp:17:19: error: 'strlen' was not declared in this scope
   int L=strlen(str);
                   ^
0_0_17632777_31626.cpp:26:27: error: 'memset' was not declared in this scope
   memset(sum,0,sizeof(sum));
                           ^